Neither Slab Consolidation nor Slab Analysis will run if slabs are less than 8 MB. (0x8900002D)

  • November 7, 2025
  • Posted by: Onsys
  • Category: Database
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You may see this error message in the Windows Event Viewer

  • ?The volume DB(M:) was not optimized because an error was encountered: Neither Slab Consolidation nor Slab Analysis will run if slabs are less than 8 MB. (0x8900002D)

What the message means

  • “Slab Consolidation/Analysis” are Windows maintenance steps for thin-provisioned LUNs. They’re skipped when the array’s slab size is < 8 MB, by design. Hence the 0x8900002D event. It’s informational, not corruption. Microsoft Support+1

Why it happens

  • Your volume is almost certainly on a thin-provisioned LUN (common on SANs/NVMe arrays). On such LUNs with small slabs, Windows disables those steps because the benefit is negligible. Microsoft Support+1

What you can do (pick one)

  1. Ignore it
    Safe to leave as-is; Windows will still do other appropriate optimizations (e.g., TRIM on SSDs). Microsoft Learn
  2. Run only TRIM/UNMAP (space reclamation) Optimize-Volume -DriveLetter M -ReTrim -Verbose This avoids slab operations and still reclaims deleted space. Microsoft Learn
  3. Silence the noise
    Replace the default “Optimize Drives” schedule with your own task that calls Optimize-Volume -ReTrim only for supported volumes.
  4. If you truly need slab consolidation
    You’d have to recreate/migrate the LUN with a slab size ≥ 8 MB (set on the storage array/VVOL when provisioning). That’s a storage-side change; not adjustable from Windows after the fact. Weigh effort vs. gain—usually not worth it for SQL log disks. HPE Support+1

Sanity checks

  • Confirm thin-provisioning:
    diskpart → list disk → select disk <n> → detail disk (look for “Thin Provisioning: Supported”). Microsoft Learn
  • Make sure TRIM is enabled (should be 0): fsutil behavior query DisableDeleteNotify ``` :contentReference[oaicite:6]{index=6}

SQL Server angle (for a log volume)

  • Log files are sequential writes; Windows defrag doesn’t help and can be skipped. Keep 64 KB NTFS allocation units, fixed-size logs, and ensure TRIM/UNMAP works; that’s what actually matters for performance/space. (General guidance + Optimize-Volume behavior.) Microsoft Learn

If you want, I can draft the one-liner Scheduled Task to run weekly -ReTrim on M: and keep the event log clean.