IBM DS3000, DS4000, and DS5000 Embedded Features and Functions

© 2009 IBM Corporation

Statements of IBM future plans and directions are provided for information purposes only. Plans and direction are subject to change without notice.

IBM DS3000, DS4000, and DS5000 Embedded Features and Functions

Ryan LeonardStorage and Solutions Architect


System Storage July 2009

Caching RAID controllers use cache for two purposes

– Buffering write requests to media– Pre-fetching read requests from media

Battery backup for minimum of 72 hours DS5100, DS5300 permanent cache backup (destage)

Read request

Write request

Cache slots allocated dynamically by controller based on demand Flexible cache block sizes – 4KB, 8KB, 16KB



Read caching Intelligent read pre-fetch algorithm

– Performs analysis of inbound read streams for sequentiality– Pre-fetch cache hits extend amount of data prefetch– Will recognize ascending, descending, and ‘sparse’ patterns

Cache Disk

Host read request



Write caching Cache mirroring for data protection Write-back and write-through modes Demand-based and age-based flushing Full-stripe write-through

– Allows full-stripe writes to bypass the cache mirroring process and write-through to media

RAID 5, 4+P

Segment

Stripe



So what is a “hardware XOR” anyway? An XOR is used in RAID 5 to calculate parity

– The XOR calculation can be performed in either hardware or software– Similar operation for RAID 6 ‘q’ information

A1 XOR A2 XOR A3 = Ap But more importantly… The hardware XOR functionality is embedded in a specialized cache memory controller

– Allows DMA transfers from host and drive side to cache independently with no processor interrupts

A1

B1

C1

Dp

A2

B2

Cp

D1

A3

Bp

C2

D2

Ap

B3

C3

D3



Configuration Flexibility Immediate Availability Format (IAF) Dynamic Array Expansion (DAE) Dynamic Volume Expansion (DVE) Dynamic RAID Migration (DRM) Dynamic Segment Sizing (DSS) HotScale DACstore



Immediate Availability Format A given logical drive, once defined via the Storage Manager, is available

almost instantaneously for usage

Array 1, RAID 5 3+P

100MB initialization region Further initialization continues in background while host reads/writes are

accepted

LUN A



Dynamic Array Expansion (DAE) Dynamically grow a given array / RAID set

– Host I/O continues during modification operation

RAID 5, 3+P

No maximum on RAID 0 or 10 on DS3/4/5000 (7.10 or higher) Maximum of 30 drives per RAID 5/6 array



Dynamic Array Expansion (DAE) Dynamically grow a given array / RAID set


RAID 5, 4+P

No maximum on RAID 0 or 10 on DS3/4/5000 (7.10 or higher) Maximum of 30 drives per RAID 5/6 array



Dynamic Volume Expansion (DVE) Dynamically grow a given logical drive / LUN within an array


Logical drives >2TB supported (w. 7.10 or higher) Available on DS3000 via CLI or Script Editor

Unused Unused Unused

C C C C

B B B B

A A A A

Unused

RAID 5, 3+P - 3 LUNs defined, A, B and C



Dynamic Volume Expansion (DVE) Dynamically grow a given logical drive / LUN within an array


Logical drives >2TB supported (w. 7.10 or higher) Available on DS3000 via CLI or Script Editor

Unused Unused Unused

C C C C

B B B B

A A A A

Unused

RAID 5, 3+P - 3 LUNs defined, A, B and C

C C C CB B B B

A A A A



Dynamic RAID Migration (DRM) Dynamically modify an array from one RAID level to another


Any to any modification Additional drives may be required to complete operation Available on DS3000 via CLI or Script Editor

RAID 5, 3+P

A1

B1

A2

B2

A3

Bp

Ap

B3



Dynamic RAID Migration (DRM) Dynamically modify an array from one RAID level to another


Any to any modification Additional drives may be required to complete operation Available on DS3000 via CLI or Script Editor

A1

B1

A2

B2

A3

Bp

Ap

B3A1 A2 A1’ A2’

B1 B2 B1’ B2’

RAID 10, 2+2



Dynamic Segment Sizing (DSS) Dynamically modify the segment size of a specific logical drive


Amount of data written to a drive before moving on to the next drive in the stripe Typically used in performance tuning Available on DS3000 via CLI or Script Editor

Drive 1 Drive 2 Drive 3 Drive 4

RAID 5, 3+P64KB 64KB 64KB 64KB



128KB 128KB 128KB 128KB

Dynamic Segment Sizing (DSS) Dynamically modify the segment size of a specific logical drive


Amount of data written to a drive before moving on to the next drive in the stripe Typically used in performance tuning Available on DS3000 via CLI or Script Editor

Drive 1 Drive 2 Drive 3 Drive 4

RAID 5, 3+P



HotScale Addition of physical storage capacity

– Host I/O can continue during drive / enclosure addition

On-demand scalability

DS3400



HotScale Addition of physical storage capacity

– Host I/O can continue during drive / enclosure addition

On-demand scalability

DS3400



DACstore 512MB reserve for drive metadata

– Array can be ‘exported’ and/or ‘imported’

Data intact relocation

Old Controllers



DACstore 512MB reserve for drive metadata

– Array can be ‘exported’ and/or ‘imported’

Data intact relocation

Old Controllers

New Controllers



Reliability, Availability, Serviceability (RAS) MediaScan

– Performs scan of physical media for unreadable blocks– All instances are logged

Advanced Rebuild– Complete a drive rebuild even after encountering unreadable sectors

Enhanced Disk Drive Predictive Fault Analysis – Monitors and logs recoverable or medium errors– May fail drives preemptively if thresholds are surpassed

Concurrent controller firmware updates Event logging and reporting

– Critical alerts via e-mail and/or SNMP

IBM DS3000, DS4000, and DS5000 Embedded Features and Functions

Documents