SSD Cache – QSAN White Paper
This article explains SSD cache for QSAN systems, covering read and read-write cache operation, pool architecture and RAID levels, cache population thresholds, tuning parameters, configuration steps, and test results. SSD cache is available on XEVO and SANOS and requires a license.
Download: SSD Cache PDF
Click here to download the SSD Cache White Paper.
Key Sections:
- Overview: Goals and benefits of SSD cache; up to 92× random read and 171× random write improvement.
- Theory of Operation:
- SSD Cache Pool Architecture: up to 4 cache pools per system; up to 8 SSDs per pool; max addressable 32 TB; up to 32 volumes can share a pool; up to 4 dedicated spares.
- RAID Levels: read cache uses NRAID+; read-write cache uses NRAID 1+ (mirrored).
- Read/Write Cases: cache miss/hit flows; write handling in read cache and read-write cache; flush behavior.
- Populating the Cache: populate-on-read/write thresholds (range 0–4; constraints by mode).
- SSD Cache Tuning: block size (1 MB/2 MB/4 MB) and thresholds by workload (Database/File System/Web Service).
- Configure SSD Cache: tutorial references for XEVO and SANOS (including trial license enablement).
- Test Results: read cache scaling with 1/2/4/8 SSDs; read-write cache with 2/4/8 SSDs; database simulation; dual-controller best practices and warm-up times.
- Apply To: XEVO firmware 2.2.0+; SANOS firmware 1.1.2+.
- References: XEVO/SANOS Software Manuals.
Critical Notes:
- LICENSE: SSD cache requires activation by license.
- CAUTION: Read-write cache carries data-loss risk if the SSD cache pool is corrupted; monitor cache pool health and allow flushing before removal.
- INFORMATION: The system does not flush cache to HDDs on shutdown/reboot.
JetStor Support
For assistance with SSD cache on JetStor systems:
๐ง [email protected]
๐ซ Submit Support Ticket