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IBM DS3000, DS4000, and DS5000 Embedded Features and Functions

IBM DS3000, DS4000, and DS5000 Embedded Features and Functions. Ryan Leonard Storage and Solutions Architect. 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

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IBM DS3000, DS4000, and DS5000 Embedded Features and Functions

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  1. IBM DS3000, DS4000, and DS5000 Embedded Features and Functions Ryan Leonard Storage and Solutions Architect

  2. 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

  3. 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 Host read request Cache Disk

  4. 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 Stripe Segment RAID 5, 4+P

  5. 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 A2 A3 Ap Bp B1 B2 B3 C1 Cp C2 C3 Dp D1 D2 D3 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

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

  7. 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 LUN A 100MB initialization region • Further initialization continues in background while host reads/writes are accepted

  8. 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

  9. Dynamic Array Expansion (DAE) • Dynamically grow a given array / RAID set • Host I/O continues during modification operation 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

  10. A A A A B B B B C C C C Dynamic Volume Expansion (DVE) • Dynamically grow a given logical drive / LUN within an array • Host I/O continues during modification operation RAID 5, 3+P - 3 LUNs defined, A, B and C Unused Unused Unused Unused • Logical drives >2TB supported (w. 7.10 or higher) • Available on DS3000 via CLI or Script Editor

  11. A A A A B B B B C C C C C C C C B B B B A A A A Dynamic Volume Expansion (DVE) • Dynamically grow a given logical drive / LUN within an array • Host I/O continues during modification operation RAID 5, 3+P - 3 LUNs defined, A, B and C Unused Unused Unused Unused • Logical drives >2TB supported (w. 7.10 or higher) • Available on DS3000 via CLI or Script Editor

  12. Dynamic RAID Migration (DRM) • Dynamically modify an array from one RAID level to another • Host I/O continues during modification operation RAID 5, 3+P A1 A2 A3 Ap B1 B2 Bp B3 • Any to any modification • Additional drives may be required to complete operation • Available on DS3000 via CLI or Script Editor

  13. Dynamic RAID Migration (DRM) • Dynamically modify an array from one RAID level to another • Host I/O continues during modification operation RAID 10, 2+2 A1 A2 A3 Ap A1 A2 A1’ A2’ B1 B2 Bp B3 B1 B2 B1’ B2’ • Any to any modification • Additional drives may be required to complete operation • Available on DS3000 via CLI or Script Editor

  14. Dynamic Segment Sizing (DSS) • Dynamically modify the segment size of a specific logical drive • Host I/O continues during modification operation RAID 5, 3+P 64KB 64KB 64KB 64KB Drive 4 Drive 3 Drive 1 Drive 2 • 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

  15. Dynamic Segment Sizing (DSS) • Dynamically modify the segment size of a specific logical drive • Host I/O continues during modification operation RAID 5, 3+P 128KB 128KB 128KB 128KB Drive 4 Drive 3 Drive 1 Drive 2 • 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

  16. HotScale • Addition of physical storage capacity • Host I/O can continue during drive / enclosure addition DS3400 • On-demand scalability

  17. HotScale • Addition of physical storage capacity • Host I/O can continue during drive / enclosure addition DS3400 • On-demand scalability

  18. DACstore • 512MB reserve for drive metadata • Array can be ‘exported’ and/or ‘imported’ Old Controllers • Data intact relocation

  19. DACstore • 512MB reserve for drive metadata • Array can be ‘exported’ and/or ‘imported’ Old Controllers New Controllers • Data intact relocation

  20. 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

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