e series training

Disk-Side and Host-Side Cabling

Lesson 2

Disk-Side Cabling Best Practices

• Cable redundantly from both controllers to both ESMs in each disk shelf

• Be consistent with ESM “in” ports• Use top-down-bottom-up cabling method

2

“In” Expansion Ports “Out” Expansion Port

E5500 Disk-Side Cabling Example

3

E5560 Controller Shelf

DE6600 Disk Shelf 1

DE6600 Disk Shelf 2

DE6600 Disk Shelf 3


4

To start the top-down loop, cable from the left EXP port on Controller A to the left “in” port on the top ESM in Disk Shelf 1.


5

Next, cable from the left EXP port on Controller B to the right “in” port on the top ESM in Disk Shelf 1.


6

Then cable from the “out” port on the top ESM in Disk Shelf 1 to the left “in” port on the top ESM in Disk Shelf 2.


7

Then cable from the “out” port on the top ESM in Disk Shelf 2 to the left “in” port on the top ESM in Disk Shelf 3 to complete the top-down cabling loop.


8

To start the bottom-up loop, cable from the right EXP port on Controller A to the left “in” port on the bottom ESM in Disk Shelf 3.


9

Next, cable from the right EXP port on Controller B to the right “in” port on the bottom ESM in Disk Shelf 3.


10

Then cable from the “out” port on the bottom ESM in Disk Shelf 3 to the left “in” port on the bottom ESM of Disk Shelf 2.


11

Then cable from the “out” port on the bottom ESM in Disk Shelf 2 to the left “in” port on the bottom ESM of Disk Shelf 1 to complete the bottom-up loop.


12


DE6600 Disk Shelf 1

DE6600 Disk Shelf 2

DE6600 Disk Shelf 3


13

To start the top-down loop, cable from the EXP port on Controller A to the left “in” port on the top ESM in Disk Shelf 1.


14

Next, cable from the “out” port on the top ESM in Disk Shelf 1 to the left “in” port on the top ESM in Drive Shelf 2.


15

Then cable from the “out” port on the top ESM in Disk Shelf 2 to the left “in” port on the top ESM in Drive Shelf 3 to complete the top-down loop.


16

To start the bottom-up loop, cable from the EXP port on Controller B to the left “in” port on the bottom ESM in Disk Shelf 3.


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18


E2700 Disk Expansion Architecture

E2700 Controllers:• Share two disk-side SAS-3 domains• Use dual-ported expansion, so external

bandwidth capability matches internal bandwidth

• Use new mini-SAS HD cable from controller to ESM

19

Mini-SAS connectors (disk shelves)

SAS Mini-HD Connectors (E2700 controllers)

Maximizing Bandwidth Performance

• Single-stack cabling– Connect both controller EXP ports to same ESM– Daisy-chain from first disk shelf to remaining shelves

• Dual-stack cabling maximizes throughput performance– Use two daisy-chain cascades– Cable one EXP port from each controller to one “in” port in

ESM in one stack– Cable second EXP port from each controller to second “in”

port in ESM in other stack

20

E2700 Disk-Side Cabling ExampleSingle Stack

21


DE6600 Disk Shelf 1

DE6600 Disk Shelf 2

DE6600 Disk Shelf 3


22

To start the top-down loop, cable from the left EXP port on Controller A to the left “in” port on the top ESM in Disk Shelf 1.


23

Next, cable from the right EXP port on Controller A to the right “in” port on the top ESM in Disk Shelf 1.


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25



26

To start the bottom-up loop, cable from the left EXP port on Controller B to the left “in” port on the bottom ESM in Disk Shelf 3.


27

Next, cable from the right EXP port on Controller B to the right “in” port on the bottom ESM in Disk Shelf 3.


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29


E2700 Disk-Side Cabling ExampleDual Stack

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DE6600 Disk Shelf

1

DE6600 Disk Shelf

2

DE6600 Disk Shelf

3

DE6600 Disk Shelf

4


31


32


33


34


35


36


37


38


39


DE6600 Disk Shelf 1

DE6600 Disk Shelf 2

DE6600 Disk Shelf 3


40

To start the top-down loop, cable from the EXP port on Controller A to the left “in” port on the top ESM in Disk Shelf 1.


41



42



43

To start the bottom-up loop, cable from the EXP port on Controller B to the left “in” port on the bottom ESM in Disk Shelf 3.


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45


Snapshot Copy-on-Write Technology

46

BaseVolume

Physical Disk Capacity

Snapshot Group

Repository

Physical disk capacity

Logical (No Actual Disk Capacity)

Copy-on-Write Example

A B C D E GF IH

A B D G I Base Volume

Snapshot

Repository

J

C

Changed Data Blocks in Base Volume

47

C F M

H

HK

E

L

F

E

Snapshot Considerations

• Performance impact considerations– Copy-on-write technology– Number of changes made to Snapshot volume– Repository full situations

• Capacity considerations– Snapshot takes less actual capacity than actual

clone copy– Repository takes some disk capacity

48

Disk Pools

To start creating disk pools, you right-click Unconfigured Capacity.Disk pools have fewer options but they have dynamic functionality:• In GUI, no choice

of individual disks attime of creation

• No RAID-level choice

• 11-disk minimum• No drawer loss

protection

49

Disk Pool Data Usage

• 4-GB d-stripe made of 10 d-pieces residing on 10 disks within pool• Intelligent algorithm defines which disks used:‒ Different set of 10 disks used for each d-stripe‒ Pseudorandom d-stripe distribution maintains balance

50

24-Drive Disk Pool

Default Preservation Capacity

• Functions like hot spares for disk pools• Set at pool creation• Can be altered later to

more or less capacity:– Minimum amount

required: 0– Maximum amount

supported: 10 disks’ worth

51

Number of Disks in Pool

Default Capacity (Number of Disks’

Worth)

11 1

12–31 2

32–63 3

64–127 4

128–191 6

192–255 7

256–384 8

24-Drive Disk Pool Becomes 23-Drive Disk Pool

Dynamic Disk Pools: Disk Failure

• For each d-stripe with data on the failed disk:‒ Segments on other disks read to recreate data‒ Data written to set of 10 disks in pool

• Rebuild operations run in parallel across all disks

52

Controller Cache

• Is dedicated to these I/O operations:– Between controllers and hosts– Between controllers and disks

• Increases controller performance:– Acts as buffer for I/O– Provides faster reads/writes than disk access– Speeds up writes when write-back caching used– Uses “prefetch” to speed up sequential reads

53

Cache Data FlowWrite Caching

Host App

Disk I/OQueue

W W R R W

? W

Response: okay

54

Cache Data FlowRequest for Data Location in Cache

Host App

Disk I/Oqueue is full.

? 0x03 0x01

0x0f

0x03

Response: okay

I/O is writtento cache.

55

Cache Data FlowRead Caching

Host App

Disk I/OQueue Full

0x03 0x01

0x0f

Response: okay

I/O is handledby cache.

Read 0x3

0x03

56

Cache Flushing

• Cache automatically “flushed” to disk:– Age based: When data times out (10-second

default)– Demand based: When cache space reaches fill

point• Start demand cache flushing: When start

percentage reached, controller starts flushing data in cache to disks

57

Cache Blocks

• Free cache: Empty cache blocks available for data

• Dirty cache: Data in cache block not yet written to disk

• Clean cache: Data in cache block consistent with data on disk

58

FreeCache

DirtyCache

CleanCache

Flushing ExampleFree Cache Area

FreeCache

DirtyCache

CleanCache

Flush threshold start = 50%Write cache is enabled.Read cache is enabled.

59

Flushing ExampleInitial I/O

60

0x0

0x1 0x4

0x3 0x6

FreeCache

DirtyCache

CleanCache


Read 0x0Read 0x1Read 0x3Read 0x4Write 0x3 (cache hit)Read 0x6

Read 0x0Read 0x1Read 0x3Read 0x4Read 0x6

Flushing ExampleDirty Cache

FreeCache

DirtyCache

CleanCache


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Read 0x3Read 0xaRead 0x1Write 0x7Write 0x3

Read 0xa0x0

0x1 0x4 0xa

0x3 0x6 0x7

Flushing ExampleStart demand cache flushing Threshold Reached

Write 0x3Write 0xaWrite 0xbWrite 0x2Read 0x3

Write 0x0Write 0x7Write 0xb

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FreeCache

DirtyCache

CleanCache


0x0

0x1 0x4 0xb0xa

0x3 0x6 0x7

Flushing ExampleAfter the Cache Flush

FreeCache

DirtyCache

CleanCache


63

0x0

0x1 0x4 0xb0xa

0x3 0x6 0x7

FreeCache

DirtyCache

CleanCache


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0x0

0x1 0x4 0xb0xa

0x3 0x6 0x7Write 0xc (uses LRU) 0x5

0xd 0xc

Flushing ExampleLeast Recently Used Queue

Read 0x5Read 0x5 (uses LRU)Read 0x0 (cache hit)

Write 0x3 (cache hit)

Read 0xd (uses LRU)

Read 0xd

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