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Creating Metadevices - (Using DiskSuite 4.2.1 Commands)

by Jef f Hunter, Sr. Database Administrator

Contents

Overview1.

Examining the Disks In Our Example2.

Partitioning the Disks3.

Metadevice State Database - (State Database Replicas)

Creating the (Initial) First Four State Database Replicas

Creating the Next Seven State Database Replicas

Creating Two State Database Replicas On the Same Slice

Query All State Database Replicas

Deleting a State Database Replica

4.

Creating a Stripe - (RAID 0)5.

Creating a Concatenation - (RAID 0)6.

Creating Mirrors - (RAID 1)

Create a Mirror From Unused Slices

Create a Mirror From a File System That Can Be UnmountedCreate a Mirror From a File System That Cannot Be Unmounted

Create a Mirror Fromswap

Create a Mirror From root(/)

7.

Creating a RAID 5 Volume - (RAID 5)8.

Creating a Trans Metadevice

Creating a Trans Metadevice for a File System That Can Be Unmounted

Creating a Trans Metadevice for a File System That Cannot Be Unmounted

Creating a Trans Metadevice Using Mirrors

9.

Creating Hot Spare10.

Overview

This article provides a comprehensive overview for creating DiskSuite metadevices (Stripes,

Concatenations, Mirrors, RAID5, and Hot Spares) using the DiskSuite command-line tools. Most of

the information can also be found in the "Solstice DiskSuite 4.2.1 User's Guide" (Part Number

806-3205-10).

Examining the Disks In Our Example

This article is all about providing definitions and examples of DiskSuite's command line tools.

Application EnablementHelping Network Providers to Enable aBetter Web Experience!

ing Metadevices - (Using DiskSuite 4.2.1 Commands) http://www.idevelopment.info/data/Unix/Solaris/SOLARIS_Creat

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For all examples in this document, I will be utilizing a Sun Blade 150 connected to a Sun StorEDGE

D1000 Disk Array containing twelve 9.1GB / 10000 RPM / UltraSCSI disk drives for a total disk

array capacity of 108GB. The disk array is connected to the Sun Blade 150 using a Dual Differential

Ultra/Wide SCSI (X6541A) host adapter. In the Sun StorEDGE D1000 Disk Array, the system

identifies the drives as follows:

Controller 1 Controller 2

c1t0d0 - (d0) c2t0d0 - (d0)

c1t1d0 - (d0) c2t1d0 - (d1)

c1t2d0 - (d1) c2t2d0 - (d1)

c1t3d0 - (d20) c2t3d0 - (d20)

c1t4d0 - (d3) c2t4d0 - (d3)

c1t5d0 - (d3) c2t5d0 - (d4)

d0 : RAID 0 - Stripe

d1 : RAID 0 - Concatenation

d20 : RAID 1 - Mirror

d3 : RAID 5

d4 : Hot Spare

From the configuration above, you can see we have plenty of disk drives to utilize for our examples!

Partitioning the Disks

Metadevices in DiskSuite are built from slices (disk partitions). If the disks you plan on using as

metadevices have not been partitioned, do so now. For the twelve 9.1GB disk drives within the

D1000 Disk Array, I use the same partition sizes and layout. I will make slice 0 a partition size of

100MB, just in case I want to attach a journaling trans metadevice later. By convention, I will use

slice 7 for the entire rest of the disk for storing the actual data. I will also use slice 7 to store the

metadb replicas for each of the tweleve disks. Also by convention, I will use slice 2 as the backuppartition.

The following is the partition tables from one of the twelve hard drives:

format>verify

Primary label contents:

Volume name = < >

ascii name =

pcyl = 4926

ncyl = 4924

acyl = 2

nhead = 27nsect = 133

Part Tag Flag Cylinders Size Blocks

0 unassigned wm 0 - 57 101.70MB (58/0/0) 2082781 unassigned wm 0 0 (0/0/0) 0

2 backup wm 0 - 4923 8.43GB (4924/0/0) 17682084

3 unassigned wm 0 0 (0/0/0) 0




7 unassigned wm 58 - 4923 8.33GB (4866/0/0) 17473806

Use theformat(1M) command to edit the partition table, label the disks, and set the volume name.


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command line in the form, mddbnn, where nn is a two-digit number given to the replica

definitions. Refer to the md.tab(4) man page for instructions on setting up replicas in that file.

Creating Two State Database Replicas On the Same Slice

#metadb -a -c2 c2t5d0s7

The -a switch tells metadb to attach a new database device. The /etc/system file is

automatically updated with the new information to tell the system to reattach the devices at

boot-time and the /etc/lvm/mddb.cf file is updated. An alternate way to create replicas is

by defining them in the /etc/lvm/md.tab file and specifying the assigned name at the

command line in the form, mddbnn, where nn is a two-digit number given to the replica

definitions. Refer to the md.tab(4) man page for instructions on setting up replicas in that file.

The -c switch is used to determine the number of database replicas that will be created on

each of the specified slices. In our case, we're creating two replicas on one slice.

Query All State Database Replicas

#metadb

flags first blk block count

a u 16 1034 /dev/dsk/c1t0d0s7a u 16 1034 /dev/dsk/c1t1d0s7


a u 16 1034 /dev/dsk/c1t4d0s7







Deleting a State Database Replica

#metadb -d c2t4d0s7

The -ddeletes all replicas that are located on the specified slice. The/etc/system file is

automatically updated with the new information and the/etc/lvm/mddb.cf file is updated.

Ok, now lets put it back!

#metadb -a c2t4d0s7

Creating a Stripe - (RAID 0)

A DiskSuite Striped Metadevice (often called just a stripe) is one of three types ofsimple

metadevices.

Striped Metadevices

Concatenated Metadevices

Concatenated Striped Metadevices

A simple metadevice is called so because they are made only from slices. Simple metadevices can

be used directly or as the basic building block for mirrors and trans metadevices.


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NOTE: Sometimes a striped metadevice is called astripe. Other times,stripe refers to the

component blocks of a striped concatenation. "To stripe" means to spread I/O requests

across disks by chunking parts of the disks and mapping those chunks to a virtual device (a

metadevice). Both striping concatenation is also classified as RAID Level 0.

The data in a striped metadevice is arranged across two or more slices. The striping alternates

equally-sized segments of data across two or more slices to form one logical storage unit. These

segments are interleaved round-robin, so that the combined space is made alternately from each

slice. Sort of like a shuffled deck of cards.

The following example creates a striped metadevice using 3 slices named/dev/md/rdsk/d0

using the metainitcommand. Of the twelve disks available in the D1000 Disk Array, I will be

using slices c1t0d0s7, c2t0d0s7, c1t1d0s7 as follows:

#metainit d0 1 3 c1t0d0s7 c2t0d0s7 c1t1d0s7 -i 32kd0: Concat/Stripe is setup

1.

Use the metastatcommand to query your new metadevice:

#metastat d0d0: Concat/Stripe

Size: 52407054 blocksStripe 0: (interlace: 64 blocks)

Device Start Block Dbase

c1t0d0s7 3591 Yes

c2t0d0s7 3591 Yes

c1t1d0s7 3591 Yes

Let's explain the details of the above example. First notice that the new striped metadevice,

d0, consists of a single stripe (Stripe 0) made of three slices (c1t0d0s7, c2t0d0s7, c1t1d0s7).

The -i option sets the interlace to 32KB. (The interlace cannot be less than 8KB, nor greater

than 100MB.) If interlace were not specified on the command line, the striped metadevice

would use the default of 16KB. When using the metastatcommand to verify our metadevice,

we can see from all disks belonging to Stripe 0, that this is a stripped metadevice. Also, that

the interlace is 32k(512 * 64 blocks) as we defined it. The total size of the stripe is

26,832,411,648 bytes (512 * 52407054 blocks).

2.

Now that we have created our simple metadevice (a stripe), we can now pretend that the

metadevice is a big partition (slice) on which we can do the usual file system things. Let's now

create a UFS file system using the newfs command. I want to create a UFS file system with an

8KB block size:

# newfs -i 8192 /dev/md/rdsk/d0

newfs: construct a new file system /dev/md/rdsk/d0: (y/n)? y/dev/md/rdsk/d0: 52407054 sectors in 14594 cylinders of 27 tracks, 133 sec

25589.4MB in 913 cyl groups (16 c/g, 28.05MB/g, 3392 i/g)

super-block backups (for fsck -F ufs -o b=#) at:32, 57632, 115232, 172832, 230432, 288032, 345632, 403232, 460832, 518432,

576032, 633632, 691232, 748832, 806432, 864032, 921632, 979232, 1036832,

1094432, 1152032, 1209632, 1267232, 1324832, 1382432, 1440032, 1497632,

1555232, 1612832, 1670432, 1728032, 1785632, 1838624, 1896224, 1953824,2011424, 2069024, 2126624, 2184224, 2241824, 2299424, 2357024, 2414624,

50909216, 50966816, 51024416, 51082016, 51139616, 51197216, 51254816,

51312416, 51370016, 51427616, 51480608, 51538208, 51595808, 51653408,51711008, 51768608, 51826208, 51883808, 51941408, 51999008, 52056608,

52114208, 52171808, 52229408, 52287008, 52344608, 52402208,

3.


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Finally, we mount the file system on /db0 as follows:

#mkdir /db0#mount -F ufs /dev/md/dsk/d0 /db0

4.

To ensure that this new file system is mounted each time the machine is started, insert the

following line into you /etc/vfstab file (all on one line with tabs separating the f ields):

/dev/md/dsk/d0 /dev/md/rdsk/d0 /db0 ufs 2 yes -

5.

Creating a Concatenation - (RAID 0)

The method used for creating a Concatenated Metadevice is very similar to that used in creating a

Striped Metadevice - both use the metainitcommand (obviously using dif ferent options) and the

same method for creating and mounting a UFS file system for.

A DiskSuite Concatenated Metadevice (often called just a Concatenation) is one of three types of

simple metadevices.

Striped Metadevices

Concatenated Metadevices

Concatenated Striped Metadevices

A simple metadevice is called so because they are made only from slices. Simple metadevices can

be used directly or as the basic building block for mirrors and trans metadevices.

The data for a concatenated metadevice is organized serially and adjacently across disk slices,

forming one logical storage unit. Many system administrators use a concatenated metadevice to get

more storage capacity by logically combining the capacities of several slices. It is possible to add

more slices to the concatenated metadevice as the demand for storage grows. A concatenated

metadevice enables you to dynamically expand storage capacity and file system sizes online! With a

concatenated metadevice you can add slices even if the other slices are currently active.

NOTE: You can also create a concatenated metadevice from a single slice. You could, for

example, create a single-slice concatenated metadevice. Later, when you need more

storage, you can add more slices to the concatenated metadevice.

The following example creates a concatenated metadevice using 3 slices named/dev/md

/rdsk/d1 using the metainitcommand. Of the twelve disks available in the D1000 Disk

Array, I will be using slices c2t1d0s7, c1t2d0s7, c2t2d0s7 as follows:

#metainit d1 3 1 c2t1d0s7 1 c1t2d0s7 1 c2t2d0s7

d1: Concat/Stripe is setup

1.

Use the metastatcommand to query your new (or in our example all) metadevices:

#metastatd0: Concat/Stripe



c1t0d0s7 3591 Yes

c2t0d0s7 3591 Yes

c1t1d0s7 3591 Yes

d1: Concat/Stripe

Size: 52410645 blocks

Stripe 0:

2.


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c2t1d0s7 3591 Yes

Stripe 1:


c1t2d0s7 3591 Yes

Stripe 2:Device Start Block Dbase

c2t2d0s7 3591 Yes

Let's explain the details of the above example. First notice that the new striped metadevice,

d1, consists of three stripes (Stripe 0, Stripe 1, Stripe 2,) each made from a single slice(c2t1d0s7, c1t2d0s7, c2t2d0s7respectively). When using the metastatcommand to verify our

metadevice, we can see this is a concatenation from the fact of having multiple Stripes. The

total size of the concatenation is 26,834,250,240 bytes (512 * 52410645 blocks).

Now that we have created our simple metadevice (a concatenation), we can now pretend that

the metadevice is a big partition (slice) on which we can do the usual file system things. Let's

now create a UFS file system using the newfs command. I want to create a UFS file system

with an 8KB block size:

# newfs -i 8192 /dev/md/rdsk/d1newfs: construct a new file system /dev/md/rdsk/d1: (y/n)? y

Warning: 1 sector(s) in last cylinder unallocated/dev/md/rdsk/d1: 52410644 sectors in 14595 cylinders of 27 tracks, 133 sec

25591.1MB in 913 cyl groups (16 c/g, 28.05MB/g, 3392 i/g)super-block backups (for fsck -F ufs -o b=#) at:

32, 57632, 115232, 172832, 230432, 288032, 345632, 403232, 460832, 518432,

576032, 633632, 691232, 748832, 806432, 864032, 921632, 979232, 1036832,1094432, 1152032, 1209632, 1267232, 1324832, 1382432, 1440032, 1497632,

51312416, 51370016, 51427616, 51480608, 51538208, 51595808, 51653408,

51711008, 51768608, 51826208, 51883808, 51941408, 51999008, 52056608,

52114208, 52171808, 52229408, 52287008, 52344608, 52402208,

3.

Finally, we mount the file system on /db1 as follows:#mkdir /db1

#mount -F ufs /dev/md/dsk/d1 /db1

4.




5.

Creating Mirrors - (RAID 1)

A mirroris a metadevice just like any other metadevice (stripe, concatenation) and is made of one

or moresubmirrors. Asubmirroris made of one or more striped or concatenated metadevices.Mirroring data provides you with maximum data availability by maintaining multiple copies of your

data (also called RAID 1).

Before creating a mirror, create the striped metadevices or concatenated metadevices that will make

up the mirror.

Any file system including root (/), swap, and /usr, or any application such as a database, can use a

mirror.

When creating a mirror, first create a one-way mirror, then attach a second submirror. This starts a


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resync operation and ensures that data is not corrupted.

To mirror an existing file system, use an additional slice of equal or greater size than the slice

already used by the mirror. You can use a concatenated metadevice or striped metadevice of two or

more slices that have adequate space to contain the mirror.

You can create a one-way mirror for a future two- or three-way mirror.

You can create up to a three-way mirror. However, two-way mirrors usually provide sufficient data

redundancy for most applications, and are less expensive in terms of disk drive costs. A three-way

mirror enables you to take a submirror offline and perform a backup while maintaining a two-way

mirror for continued data redundancy.

Use the same size slices when creating submirrors. Using different size slices creates unused space in

the mirror.

Avoid having slices of submirrors on the same disk. Also, when possible, use disks attached to

different controllers to avoid single points-of-failure. For maximum protection and performance,

place each submirror on a different physical disk and, when possible, on different disk controllers.

For further data availability, use hot spares with mirrors.

Adding additional state database replicas before creating a mirror can increase the mirror's

performance. As a general rule, add one additional replica for each mirror you add to the system.

If possible create mirrors from disks consisting of the same disk geometries. The historical reason is

that UFS uses disk blocks based on disk geometries. Today, the issue is centered around

performance: a mirror composed of disks with different geometries will only be as fast as its slowest

disk.

This section will contain the following five examples for creating different types of two-way mirrors:

Create a Mirror From Unused Slices1.

Create a Mirror From a File System That Can Be Unmounted2.Create a Mirror From a File System That Cannot Be Unmounted3.

Create a Mirror From swap4.

Create a Mirror From root (/)5.

To perform the above mirror examples, I will be using the two disks: c1t3d0 and c2t3d0. After

creating each two-way mirror example, I will be deleting the newly created mirror to get ready for

the next example.

Create a Mirror From Unused Slices

Use the metainitcommand to create two metadevices - each new concatenation metadevice(d21 and d22) consists of a single stripe (Stripe 0) made of one slice (c1t3d0s7 and

c2t3d0s7) respectively:

#metainit d21 1 1 c1t3d0s7




1.

Using the metainit -m command to create a one-way mirror (namedd20) from one of the

submirrors.

2.


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#metainit d20 -m d21

d20: Mirror is setup

Finally, use the metattach command to create the two-way mirror (namedd20) from the

second submirror (d22).

#metattach d20 d22

d20: submirror d22 is attached

We now have a two-way mirror, d20. The metainitcommand was first used to create the two

submirrors (d21 and d22), which are actually concatenations. The metainit -m command was

then used to create a one-way mirror from the d21 concatenation. We then used the

metattach command to attach d22, creating a two-way mirror and causing a mirror resync.

(Any data on the attached submirror is overwritten by the other submirror during the

resync.) The system verifies that the objects are set up.

3.

Now that we have created our simple metadevice (a mirror), and the mirror resync is

complete, we can now pretend that the metadevice is just a regular partition (slice) on which

we can do the usual file system things. Let's now create a UFS file system using the newfs

command. I want to create a UFS file system with an 8KB block size:

# newfs -i 8192 /dev/md/rdsk/d20newfs: construct a new file system /dev/md/rdsk/d20: (y/n)? yWarning: 1 sector(s) in last cylinder unallocated

/dev/md/rdsk/d20: 17470214 sectors in 4865 cylinders of 27 tracks, 133 sect8530.4MB in 305 cyl groups (16 c/g, 28.05MB/g, 3392 i/g)

super-block backups (for fsck -F ufs -o b=#) at:

32, 57632, 115232, 172832, 230432, 288032, 345632, 403232, 460832, 518432,576032, 633632, 691232, 748832, 806432, 864032, 921632, 979232, 1036832,

1094432, 1152032, 1209632, 1267232, 1324832, 1382432, 1440032, 1497632,

1555232, 1612832, 1670432, 1728032, 1785632, 1838624, 1896224, 1953824,

16321568, 16379168, 16436768, 16494368, 16547360, 16604960, 16662560,

16720160, 16777760, 16835360, 16892960, 16950560, 17008160, 17065760,

17123360, 17180960, 17238560, 17296160, 17353760, 17411360, 17468960,

4.


#mkdir /db20#mount -F ufs /dev/md/dsk/d20 /db20

5.




6.

The volume, /db20 is now ready for use!7.

Create a Mirror From a File System That Can Be Unmounted

The procedures document in this section can be used to mirror a file system that can be

unmounted during normal operation. While most file systems can be unmounted during

normal operation, there are some which cannot be unmounted like root/, /usr, /opt or

swap. Procedures for mirroring those file systems which cannot be unmounted during normal

operation are documented in the next section.

1.

First, identify the slice that contains the file system to me mirrored. For this example, I will be2.


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using /dev/dsk/c1t3d0s7 that contains an existing file system that I want to have mirrored.

This is a file system that can be unmounted.

The slice /dev/dsk/c1t3d0s7 contains an 8K UFS file system and is mounted on /db20.

Use the metainit -fto put the mounted file system's slice in a single slice (one-way)

concat/stripe. (This will be submirror1) The following command creates one stripe that

contains one slice. The new metadevice will be namedd21:

#metainit -f d21 1 1 c1t3d0s7d21: Concat/Stripe is setup

3.

Create a second concat/stripe. (This will besubmirror2)



4.

Use the metainit -m command to create a one-way mirror withsubmirror1.



5.

Unmount the file system

# umount /db20

6.

Edit the /etc/vfstab file so that the existing file system entry now refers to the newly

created mirror. In the following example snippet, I commented out the original entry for the

c1t3d0s7 slice and added a new entry that refers to the newly created mirrored metadevice

(d20) to be mounted to /db20:

# /dev/dsk/c1t3d0s7 /dev/rdsk/c1t3d0s7 /db20 ufs 2 yes -/dev/md/dsk/d20 /dev/md/rdsk/d20 /db20 ufs 2 yes -

7.

Remount the file system:

#mount /db20

8.

Use the metattach command to attachsubmirror2

#metattach d20 d22d20: submirror d22 is attached

9.

After attaching d22 (submirror2), this triggers a mirror resync. Use the metastatcommand to

view the progress of the mirror resync:

#metastat d20d20: Mirror

Submirror 0: d21State: Okay

Submirror 1: d22

State: Resyncing Resync in progress: 15 % done

Pass: 1

Read option: roundrobin (default)

Write option: parallel (default)


d21: Submirror of d20

State: OkaySize: 17470215 blocks

Stripe 0:

10.


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Device Start Block Dbase State Hot Spare

c1t3d0s7 3591 Yes Okay


State: ResyncingSize: 17470215 blocks

Stripe 0:

Device Start Block Dbase State Hot Sparec2t3d0s7 3591 Yes Okay

From the above example, we didn't create a multi-way mirror right away. Rather, we created

a one-way mirror with the metainitcommand then attach the additional submirrors with the

metattach command. When the metattach command is not used, no resync operations occur

and data could become corrupted. Also, do not create a two-mirror for a file system without

first unmounting the file system , editing the /etc/vfstab file to reference the mirrored

metadevice, and then mount the file system to the new mirrored metadevice before attaching

the second submirror.

11.

Create a Mirror From a File System That Cannot Be Unmounted

The procedures in this section can be used to mirror file systems, such as/usr and /opt -those that cannot be unmounted during normal system usage.

1.

First, identify the slice that contains the file system to me mirrored. For this example, I will be

using the /usr file system which is located on c0t0d0s6 that I want to have mirrored. This is

a file system that cannot be unmounted.

The slice /dev/dsk/c0t0d0s6 contains an 8K UFS file system and is mounted on /usr. This

will be made into submirror1 (d21) using the metainitcommand. For submirror2 (to make our

two-way mirror) I will be using /dev/dsk/c2t3d0s7.

2.

Use the metainit -fto put the mounted file system's slice in a single slice (one-way)




3.


#metainit d22 1 1 c2t3d0s7d22: Concat/Stripe is setup

4.


#metainit d20 -m d21d20: Mirror is setup

5.

Edit the /etc/vfstab file so that the file system (/usr) now refers to the newly created

mirror. In the example snippet, I commented out the original entry for the c0t0d0s6 slice and

added a new entry that refers to the newly created mirror to be mounted to/usr:

# /dev/dsk/c0t0d0s6 /dev/rdsk/c0t0d0s6 /usr ufs 1 no -

/dev/md/dsk/d20 /dev/md/rdsk/d20 /usr ufs 1 no -

6.

Reboot the system7.


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# reboot



8.




Submirror 0: d21

State: OkaySubmirror 1: d22

State: Resyncing

Resync in progress: 8 % done

Pass: 1

Read option: roundrobin (default)Write option: parallel (default)



State: Okay

Size: 16781040 blocksStripe 0:


c0t0d0s6 0 No Okay

d22: Submirror of d20State: Resyncing


Stripe 0:



9.

From the above example, we didn't create a multi-way mirror right away for the/usr file

system. Rather, we created a one-way mirror with the metainitcommand then attach the

additional submirrors with the metattach command (after rebooting the server). When the

metattach command is not used, no resync operations occur and data could become

corrupted. Also, do not create a two-mirror for a file system without first editing the

/etc/vfstab file to reference the mirror metadevice and then rebooting the server before

attaching the second submirror.

10.

Create a Mirror From swap

The procedures in this section of the documentation can be used to mirror theswap file

system. Theswap file system, like /usr and /opt, cannot be unmounted during normalsystem usage.

1.

First, identify the slice that contains theswap file system to me mirrored. For this example, the

swap file system it is located on c0t0d0s3 that I want to have mirrored. This is a file system

that cannot be unmounted.

The slice /dev/dsk/c0t0d0s3 contains theswap file system. This will be made into

submirror1 (d21) using the metainitcommand. For submirror2 (to make our two-way mirror) I

will be using /dev/dsk/c2t3d0s7.

2.


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Use the metainit -fto put the mounted file system (swap) in a single slice (one-way)




3.



4.




5.

Edit the /etc/vfstab file so that theswap file system now refers to the newly created mirror.

In the example snippet, I commented out the originalswap entry for the c0t0d0s3 slice and

added a new entry that refers to the newly created mirror:

# /dev/dsk/c0t0d0s3 - - swap - no -

/dev/md/dsk/d20 - - swap - no -

6.

Reboot the system

# reboot

7.



8.




Submirror 0: d21

State: Okay

Submirror 1: d22

State: Resyncing

Resync in progress: 32 % donePass: 1

Read option: roundrobin (default)Write option: parallel (default)



State: Okay

Size: 2101200 blocksStripe 0:


c0t0d0s3 0 No Okay


State: Resyncing


Stripe 0:

Device Start Block Dbase State Hot Sparec2t3d0s7 3591 Yes Okay

9.


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Verify that theswap file system is mounted on the d20 metadevice:

# swap -lswapfile dev swaplo blocks free

/dev/md/dsk/d20 85,20 16 2101184 2101184

10.

From the above example, we didn't create a multi-way mirror right away for theswap file

system. Rather, we created a one-way mirror with the metainitcommand then attach the

additional submirrors with the metattach command (after rebooting the server). When the

metattach command is not used, no resync operations occur and data could becomecorrupted. Also, do not create a two-mirror for a file system without first editing the

/etc/vfstab file to reference the mirror metadevice and then rebooting the server before

attaching the second submirror.

11.

Create a Mirror From root (/)

Use the following procedures to mirror the root(/) file system on a SPARC system.

NOTE: The task for using the command-line to mirror root (/) on an x86 system is

different from the task used for a SPARC system.

When mirroring root(/), it is essential that you record the secondary root slice name to

reboot the system if the primary submirror fails. This information should be written down,

not recorded on the system, which may not be available in the event of a disk failure.

1.

Use the metainit -fto put the root (/) slice in a single slice (one-way) concat. (submirror1).

(This will be submirror1)

The following command creates one stripe that contains one slice. The new metadevice will

be named d21:


2.



3.




4.

Run the metarootcommand. This will update both the /etc/vfstab and /etc/system files

to reflect the new rootslice the system will boot from:

#metaroot d20

5.

Run the lockfs command:

# lockfs -fa

6.

Reboot the system

# reboot

7.


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8.

Record/document the alternate boot path in the case of failure.

# ls -l /dev/rdsk/c0t2d0s0

lrwxrwxrwx 1 root root 42 Nov 12 09:35 /dev/rdsk/c0t2d0s0 -> ../../devices/pc

9.

NOTE: The -f option forces the creation of the first concatenation, d21, which contains

the mounted file system root (/) on /dev/dsk/c0t0d0s0. The second concatenation, d22,

is created from /dev/dsk/c0t2d0s0. (This slice must be the same size or greater than

that of d21) The metainit command with the -m option creates the one-way mirrord20

using the concatenation containing root (/). Next, the metarootcommand edits the

/etc/vfstab and /etc/systemfiles so that the system may be booted with the root file

system (/) on a metadevice. (It is a good idea to run lockfs -fa before rebooting.) After

a reboot, the submirrord22 is attached to the mirror, causing a mirror resync. (The system

verifies that the concatenations and the mirror are set up, and that submirrord22 is

attached.) The ls -l command is run on the root raw device to determine the path to the

alternate root device in case the system needs to be booted from it.

Creating a RAID5 Volume - (RAID 5)

A RAID5 metadevice uses storage capacity equivalent to one slice in the metadevice to store

redundant information about user data stored on the remainder of the RAID5 metadevice's slices.

The redundant information is distributed across all slices in the metadevice. Like a mirror, a RAID5

metadevice increases data availability, but with a minimum of cost in terms of hardware.

The system must contain at least three state database replicas before you can create RAID5

metadevices.

A RAID5 metadevice can only handle a single slice failure.

Follow the 20-percent rule when creating a RAID5 metadevice: because of the complexity of parity

calculations, metadevices with greater than about 20 percent writes should probably not be RAID5

metadevices. If data redundancy is needed, consider mirroring.

There are drawbacks to a slice-heavy RAID5 metadevice: the more slices a RAID5 metadevice

contains, the longer read and write operations will take if a slice fails.

A RAID5 metadevice must consist of at least three slices.

A RAID5 metadevice can be grown by concatenating additional slices to the metadevice. The new

slices do not store parity information, however they are parity protected. The resulting RAID5

metadevice continues to handle a single slice failure.

The interlace value is key to RAID5 performance. It is configurable at the time the metadevice is

created; thereafter, the value cannot be modified. The default interlace value is 16 Kbytes. This is

reasonable for most applications.

Use the same size disk slices. Creating a RAID5 metadevice from different size slices results in

unused disk space in the metadevice.


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Do not create a RAID5 metadevice from a slice that contains an existing file system. Doing so will

erase the data during the RAID5 initialization process.

RAID5 metadevices cannot be striped, concatenated, or mirrored.

The following example creates a RAID 5 metadevice using 3 slices that will be named

/dev/md/rdsk/d3 with the metainitcommand. Of the twelve disks available in the D1000

Disk Array, I will be using slices c1t4d0s7, c2t4d0s7, c1t5d0s7 as follows:

#metainit d3 -r c1t4d0s7 c2t4d0s7 c1t5d0s7d3: RAID is setup

Let's explain the details of the above example. The RAID5 metadeviced3 is created with the

-r option from three slices. Because no interlace is specified,d3 uses the default of 16

Kbytes. The system verifies that the RAID5 metadevice has been set up, and begins

initializing the metadevice.

1.

Use the metastatcommand to query your new RAID5 metadevices. After running the above

command, the metadevice will go through an initialization state. This may take several

minutes to complete. When using the metastatcommand, you will be able to view how far of

the initialization is completed. You must wait for the initialization to finish before you can use

the new RAID5 metadevice. The following screenshot shows the RAID5 metadevice duringits initialization phase:

#metastat d3

d3: RAID

State: Initializing Initialization in progress: 22% done

Interlace: 32 blocks


Original device:

Size: 34939712 blocksDevice Start Block Dbase State Hot Spare

c1t4d0s7 3921 Yes Initializing

c2t4d0s7 3921 Yes Initializingc1t5d0s7 3921 Yes Initializing

When the disks within the RAID5 metadevice are completed with their initialization phase,

this is what it will look like:

#metastat d3

d3: RAIDState: Okay

Interlace: 32 blocks

Size: 34936839 blocksOriginal device:



c1t4d0s7 3921 Yes Okayc2t4d0s7 3921 Yes Okay


2.

Now that we have created our RAID5 metadevice, we can now pretend that the metadevice is

a big partition (slice) on which we can do the usual file system things. Let's now create a UFS

file system using the newfs command. I want to create a UFS file system with an 8KB block

size:

# newfs -i 8192 /dev/md/rdsk/d3

newfs: construct a new file system /dev/md/rdsk/d3: (y/n)? yWarning: 1 sector(s) in last cylinder unallocated

/dev/md/rdsk/d3: 34936838 sectors in 9729 cylinders of 27 tracks, 133 sect

3.


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17059.0MB in 609 cyl groups (16 c/g, 28.05MB/g, 3392 i/g)

super-block backups (for fsck -F ufs -o b=#) at:

32, 57632, 115232, 172832, 230432, 288032, 345632, 403232, 460832, 518432,

576032, 633632, 691232, 748832, 806432, 864032, 921632, 979232, 1036832,

1094432, 1152032, 1209632, 1267232, 1324832, 1382432, 1440032, 1497632,

34016288, 34073888, 34131488, 34189088, 34246688, 34304288, 34361888,34419488, 34477088, 34534688, 34592288, 34649888, 34707488, 34765088,

34822688, 34880288, 34933280,


#mkdir /db3

#mount -F ufs /dev/md/dsk/d3 /db3

4.




5.

Creating a Trans Metadevice

A trans metadevice enables UFS logging, which is the process of recording UFS updates in a log

before the updates are applied to the UNIX file system. A trans metadevice can increase overall file

system availability after reboot, because it reduces the amount of time fsck(1M) has to run when the

system reboots.

The trans metadevice normally has two devices: the master device and the logging device. The

master contains the file system that is being logged. The logging device contains the log and can be

shared by several file systems. It is a sequence of records, each of which describes a change to a file

system. Both the master device and the logging device can be a slice or a metadevice.

Though logs can be shared between file systems, heavily-used file systems should have their own

logging device.

Small file systems with mostly read operations probably do not need to be logged.

Any UFS, except root (/), can be logged.

Even if you don't have an available slice for a logging device, you can still set up a trans metadevice

without a logging device. This is useful if you plan to enable logging on exported file systems, but do

not have an available slice for the logging device at this time.

Before creating trans metadevices, identify the slices or metadevice to be used as the master devices

and logging devices.

Avoid placing logs on heavily-used disks.

Do not use a RAID5 metadevice as a logging device. Instead, use a mirror for data redundancy.

Logs (the logging device) can be placed on a slice that already contains a state database replica.

Plan on using one megabyte of log space as a minimum, and an additional one megabyte of log

space per 100 megabytes of file system data, up to a maximum log size of 64 Mbytes. Logs greater

than 64 Mbytes waste space.


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The master devices and logging devices of the same trans metadevice should be located on separate

drives and possibly separate controllers.

CAUTION: Mirroring logging devices is strongly recommended. Losing the data in a

logging device because of device errors can leave a file system in an inconsistent state

which fsck(1M) may not be able to fix without user intervention. Using a mirror for the

master device is a good idea to ensure data redundancy.

This section will contain the following four examples for creating different types of transmetadevices:

Creating a Trans Metadevice for a File System That Can Be Unmounted1.

Creating a Trans Metadevice for a File System That Cannot Be Unmounted2.

Creating a Trans Metadevice Using Mirrors3.

If you notice the section of this document entitled, "Partitioning the Disks", you will see that, for

all twelve 9.1GB disk drives within the D1000 Disk Array, I made slice 0 a partition size of 100MB,

just in case I want to attach a journaling trans metadevice later. Well, that time is now, and I will be

using slice 0 of the above selected disks.

Creating a Trans Metadevice for a File System That Can Be Unmounted

The following example creates a trans metadevice that can be unmounted. The UFS file

system (the master device) that will be logged is a stripped metadevice (RAID 0)

named (/dev/md/rdsk/d0). The UFS file system bound to this metadevice is/db0.

(Keep in mind that the master device can also be a regular slice; it does not have to be

a metadevice!)

The logging device will be created on a 100M slice/dev/dsk/c1t0d0s0.

In this example, the Trans Metadevice will be namedd5.

First, unmount the master device file system:

# umount /db0

1.

Create the trans metadevice with the metainitcommand. In the following

command, we will create a tran metadevice namedd5 using the -toption. The

metadevice, d0 is the master device, while the slice c1t0d0s0 will contain the

logging device.

#metainit d5 -t d0 c1t0d0s0

d5: Trans is setup

2.

Next, edit the /etc/vfstab file so that the file system references the newly

created trans metadevice, (d5), each time the machine is started. Change the

entry in the file that would mount the UFS file system to the /dev/md/rdsk/d0

metadevice: (all on one line with tabs separating the fields):

# /dev/md/dsk/d0 /dev/md/rdsk/d0 /db0 ufs 2 yes -/dev/md/dsk/d5 /dev/md/rdsk/d5 /db0 ufs 2 yes -

3.

Finally, mount the file system:

#mount /db0

4.


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Use the metastatcommand to query information on the new trans metadevice:

#metastat d5d5: Trans

State: Okay

Size: 52407054 blocksMaster Device: d0

Logging Device: c1t0d0s0

d0: Concat/Stripe




c2t0d0s7 3591 Yes Okayc1t1d0s7 3591 Yes Okay

c1t0d0s0: Logging device for d5State: Okay

Size: 202637 blocks

Logging Device Start Block Dbase

c1t0d0s0 5641 No

5.

Logging becomes effective for the file system when it is remounted.

On subsequent reboots, instead of checking the file system,fsckdisplays a

logging message for the trans metadevice:

reboot...

/dev/md/rdsk/d5: is logging.

6.

Creating a Trans Metadevice for a File System That Cannot Be Unmounted

The following example creates a trans metadevice that cannot be unmounted during

normal system operation. The UFS file system (the master device) that will be logged is

/usr. The /usr file system is currently mounted on /dev/dsk/c0t0d0s6. The logging

device will be created on slice /dev/dsk/c1t1d0s0.

First, create the trans metadevice with the metainitcommand. Slice /dev/dsk

/c0t0d0s6 contains the /usr file system. The slice to contain the logging device

is /dev/dsk/c1t1d0s0. Because /usr cannot be unmounted, the metainit

command is run with the -f option to force the creation of the trans device,d6.

#metainit -f d6 -t /dev/dsk/c0t0d0s6 c1t1d0s0

d6: Trans is setup

1.

Edit the /etc/vfstab file so that the /usr file system now refers to the newly

created trans metadevice. In the example snippet, I commented out the originalentry for the /usr file system (c0t0d0s6) and added a new entry that refers to

the newly created trans metadevice to be mounted to /usr:

# /dev/dsk/c0t0d0s6 /dev/rdsk/c0t0d0s6 /usr ufs 1 no/dev/md/dsk/d6 /dev/md/rdsk/d6 /usr ufs 1 no -

2.

Reboot the system

# reboot

3.

Logging becomes effective for the file system when the system is rebooted!4.


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Finally, lets check the status of the new Trans Metadevice:

#metastat d6d6: Trans

State: Okay

Size: 16781040 blocksMaster Device: c0t0d0s6

Logging Device: c1t1d0s0

Master Device Start Block Dbase

c0t0d0s6 0 No

c1t1d0s0: Logging device for d6

State: Okay

Size: 202637 blocks

Logging Device Start Block Dbase

c1t1d0s0 5641 No

5.

Creating a Trans Metadevice Using Mirrors

You can (and should!!!) increase data availability of a trans metadevice by using

mirrors for the master AND logging devices. Failure to mirror the logging device could

result in significant data loss if the logging slice experiences errors. If you are mirroringthe logging device, it is a good idea that the master device be a mirror also.

This is an example of how to create a Trans Metadevice where both the master

device and the logging device is a mirror.

1.

To start off with, we already have a mirrored metadevice namedd20 which is

mounted on /db20. This will be the file system we want to have being logged.

(Not that it matters for this example, but the mirrored metadevice is a two-way

mirror that contains two submirrors:d21 and d22.)

2.

Next, make a mirror (lets name this one d30) to be used as the logging device. It

will be a two-way mirror containing submirrors d31 and d32.

3.

First, unmount the file system you want to have logged:

# umount /db20

4.

Next, use the metainitcommand with the -t option to create the Trans

Metadevice, d40:

#metainit d40 -t d20 d30d40: Trans is setup

5.

Edit the /etc/vfstab file so that the /db20 file system now refers to the newly

created trans metadevice. In the example snippet, I commented out the originalentry for the /db20 file system (/dev/md/dsk/d0) and added a new entry that

refers to the newly created trans metadevice to be mounted to/db20:

# /dev/md/dsk/d0 /dev/md/rdsk/d0 /db0 ufs 2 yes -/dev/md/dsk/d40 /dev/md/rdsk/d40 /db0 ufs 2 yes -

6.

Logging becomes effective for the file system when the file system is remounted!7.

On subsequent file system remounts or system reboots, instead of checking the

file system,fsckdisplays a logging message for the metadevice:

8.


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# reboot

.../dev/md/rdsk/d40: is logging

Creating a Hot Spare

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