Auto Tiering – QSAN White Paper

This article summarizes auto tiering for QSAN systems (XEVO, SANOS). It explains tier categories (SSD/SAS/NL-SAS), architecture and policies, statistics-based relocation, transfer from thick/thin pools, SSD cache vs. auto tiering, configuration, and best practices.

Download: Auto Tiering PDF

Click here to download the Auto Tiering White Paper.

Key Sections:

  • Overview: Goal of balancing performance and cost with hybrid tiers.
  • Tier Categories: Tier 1 SSD (extreme performance), Tier 2 SAS HDD (performance), Tier 3 NL-SAS HDD (capacity); Tier 4 SATA (single-controller only, not recommended).
  • Flexible RAID & Disk Configurations: Different RAID levels and disk counts per tier.
  • Theory of Operation: Thin-provisioned pool; 1 GB allocation units; reserve ~10% free space on higher tiers; pool parameters (up to 32 disk groups; 64 disks/group; 256 disks/pool; 64 TB per disk group; 256 TB per pool; up to 1,024 TB across pools).
  • Intelligent Mechanism: Hourly statistics with half-life weighting (~24 h), hotness ranking, and relocation by scheduled window and rate (Fast/Medium/Slow).
  • Tiering Policies: Auto Tiering (default); Start Highest then Auto Tiering; Highest Available Tier; Lowest Tier; No Data Movement.
  • Transfer to Auto Tiering Pool: Convert existing thick/thin pools by adding mixed-type disk groups; capacity behavior differs for thick vs. thin.
  • SSD Cache vs. Auto Tiering: Capacity contribution, durability, and short- vs. long-term effectiveness.
  • Configure Auto Tiering Pools: Tutorial references for XEVO/SANOS.
  • Best Practice: Planning guidance (e.g., SSD ~10–15% of total), relocation scheduling, and example cases (Video Editing, VMware, Sudden Reaction).
  • Conclusion & Appendix: Apply To and references.

Critical Notes:

  • INFORMATION: Auto tiering is a licensed feature on XEVO and SANOS.
  • CAUTION: Transferring a pool to auto tiering is irreversible.
  • INFORMATION: Snapshots reside on the lowest tier and may limit performance.
  • CAUTION: In dual-controller systems using SATA SSDs, each SSD is limited to ~270 MB/s due to the MUX board.

Apply To

XEVO firmware 2.2.0+; SANOS firmware 1.2.0+.

JetStor Support

For assistance with auto tiering on JetStor systems:
๐Ÿ“ง [email protected]
๐ŸŽซ Submit Support Ticket