WAFL Internals

Appendix A

Data ONTAP 8.0 7-Mode Administration

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Module Objectives

By the end of this module, you should be able to:Describe how data is structure within a WAFL®

file system on a traditional volumeDescribe how data is structure within a WAFL

file system in a flexible on a 32-bit aggregateDescribe how data is structure within a WAFL

file system in a flexible on a 64-bit aggregate

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WAFL Structure

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WAFL

WAFL– Is the file system in Data ONTAP– Stores metadata in files and uses a buffer tree

structure– Allows it to write metadata files and blocks

anywhere on diskWrite Anywhere File Layout

– More flexible than traditional file systems because metadata not at fixed locations on diskOne exception is the root inode

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WAFL Block Structure

WAFL organizes data into blocks– Use vol status -b to verify block sizesystem> vol status -bVolume Block Size (bytes) Vol Size (blocks) FS Size (blocks)------ ------------------ ----------------- ---------------- vol0 4096 7058256 7058256

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WAFL Structure

WAFL is structured into volumes

Aggregate

vol1

vol1

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WAFL and Inodes

WAFL organizes some metadata into inodesAn inode is:

– A collection of information about a file or directory

– Holds information including: time/date stamp, size, UNIX® permissions, Windows® ACL, and so on

– 192 bytes of data– Placed within a file called the inode file (inofile)

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vol1

WAFL Structure

Every volume has a root inode– The starting point of the inode “tree”

Aggregate

vol1

root inode

volinfoblock 1

volinfo block 2

fsinfo block 255

fsinfo block

0. . .

Active file system

Snapshotdefinitions

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vol1

Inode information is held in the inode file (inofile), a hidden system file

WAFL Structure (Cont.)

Aggregate

vol1

root inode

Inode file

192 Byte inode

4096 Bytes blocks

0 21. . . 20

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vol1

For files that are < 65 B, the data is stored within the inode file

Level 0

Aggregate

vol1

root inode

Inode file

Small file data inside the 192

Byte inode

Small file inode

0 . . . 20

4-KB Block

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vol1

For files that are > 64 B but <= 64 KB, a level 1 inode structure is used

Level 1 In Traditional Volumes

vol1

root inode

Inode file

32-bit pointersfile inode

. . .0 1 15 4 Bytes

DirectData Block

DirectData Block

DirectData Block

4-KB Block

0 . . . 20

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Traditional Volume

Traditional Volumes Data Structure

Disk

Physical Block

Number500 block

number

Volume Block

Number500 block

number

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vol1

For files that are > 64 B but <= 32 KB, a level 1 inode structure is used

Level 1 In 32-Bit Aggregates

32-bit Aggregate

vol1

root inode

Inode file

32-bit pointersfile inode

. . .0 2 x 4 bytes

DirectData Block

DirectData Block

DirectData Block

4-KB Block

0 . . . 20

1 7

NOTE: 2 x 4 bytes because of separation of physical and virtual VBN

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Aggregate

Flexible Volumes Data Structure

Disk

PvBN456 block

number

vVBN500 block

number

vol1 vol2Disk

vVBN500 block

number

PvBN123 block

number

Physical Virtual Block Number (PvBN) and Virtual Volume Block Number

(vVBN)

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vol1

For files that are > 64 B but <= 16 KB, a level 1 inode structure is used

Level 1 In 64-Bit Aggregates

64-bit Aggregate

vol1

root inode

Inode file

64-bit pointersfile inode

. . .0 2 x 8 bytes

DirectData Block

DirectData Block

4-KB Block

0 . . . 20

3

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vol1

For files that are > 64 KB but <= 64 MB, a level 2 inode structure is used

Level 2 In Traditional Volumes

root inode

Inode file

. . .

DirectData Block

DirectData Block

DirectData Block

Up to 16 indirect blocks

. . . 10230 . . . 10230

0 1 15

0 . . . 20

32-bit pointersfile inode

vol1

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vol1

For files that are > 32 KB but <= 16 MB, a level 2 inode structure is used

Level 2 In 32-Bit Aggregates

32-bit Aggregate

vol1

root inode

Inode file

32-bit pointersfile inode

. . .0

0 . . . 20

1 7

DirectData Block

DirectData Block

DirectData Block

Up to 8 indirect blocks

. . . 5110 . . . 5110

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vol1

For files that are > 16 KB but <= 4 MB, a level 2 inode structure is used

Level 2 In 64-Bit Aggregates

64-bit Aggregate

vol1

root inode

Inode file

64-bit pointersfile inode

. . .0

0 . . . 20

3

DirectData Block

DirectData Block

DirectData Block

Up to 4 indirect blocks

. . . 2550 . . . 2550

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vol1

Each directory inode points to at least one 4-KB block that holds the metadata for the block

Directories

Aggregate

vol1

root inode

Inode file

Directory inode

4-KB Block Entries Chunks

An array of entries containing 128 rows of 12 bytes

An array of 160 sixteen-byte name chunks

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Module Summary

In this module, you should have learned to: Describe how data is structure within a WAFL®

file system on a traditional volumeDescribe how data is structure within a WAFL

file system in a flexible on a 32-bit aggregateDescribe how data is structure within a WAFL

file system in a flexible on a 64-bit aggregate