Skip to main content
Version: 3.6

Optimize Cache Performance with Auto-Tune Cache Migration Threshold

Enable auto-tune and optimize your cache performance by auto-tuning cache tunables like migration threshold.

Enable auto-tune​

Use the pxctl cluster options update command with the --poolcache flag to enable auto-tune.

pxctl cluster options update --poolcache on

This enables auto-tuning with default thresholds.

  • Minimum dirty threshold: 33%
  • Maximum dirty threshold: 67%

Custom thresholds​

You can specify custom thresholds using poolcache option.

pxctl cluster options update --poolcache on,<min_dirty>,<max_dirty>

For example, to set thresholds to 40% minimum and 75% maximum:

pxctl cluster options update --poolcache on,40,75

Threshold limits​

ParameterDefaultMinimumMaximum
min_dirty33%10%(must be < max_dirty)
max_dirty67%(must be > min_dirty)90%
info

If you specify invalid thresholds (min >= max, or out of limits), Portworx will override them with default values.

Disable auto-tune​

To disable auto-tuning, use poolcache option.

pxctl cluster options update --poolcache off

You can manually tune migration_threshold by configuring storage pool cache.

Check auto-tune status​

View the current auto-tune configuration and state:

pxctl service pool cache status <pool_id>

Look for these fields:

  • AutoTune: Whether auto-tuning is enabled
  • DirtyState: Current state (low, optimal, or high)
  • MinDirtyPercent: Configured minimum threshold
  • MaxDirtyPercent: Configured maximum threshold

Example output:

PX Cache Configuration and Status:
Pool ID:  0
        Enabled:  true
        ...
        DirtyBlocks: 2500
        TotalBlocks: 8564
        ...
        DirtyState: optimal
        AutoTune: true
        MinDirtyPercent: 33
        MaxDirtyPercent: 67

In this example, dirty blocks are 2500/8564 = ~29%, which would be below the 33% threshold (DirtyState: low).

View current cluster options​

Check the current auto-tune configuration for the cluster:

pxctl cluster options list

Look for the PoolCacheConfig section in the output.

Best practices for auto-tune pool cache​

  1. Start with defaults. The default thresholds (33%, 67%) work well for most workloads.
  2. Monitor before tuning. Use pxctl service pool cache status to understand your workload patterns before adjusting thresholds.
  3. Workload considerations:
    • For bursty write workloads, consider lowering the max threshold to trigger earlier cleanup
    • For steady-state workloads, default thresholds are usually optimal
  4. Don't over-tune. Frequently changing thresholds can cause unstable behavior

Troubleshooting storage pool cache configuration​

Cache is always in "high" state​

This indicates your workload consistently generates more writes than the backing storage can absorb. Consider:

  • Adding more cache capacity
  • Using faster backing storage
  • Reducing write load

Cache is always in "low" state​

This indicates your cache is larger than needed for your workload. This is not a problem - it just means you have headroom for burst activity.

Auto-tune not taking effect​

Verify auto-tune is enabled:

  1. Check cluster options: pxctl cluster options list
  2. Verify pool status shows AutoTune: true
  3. Ensure caching is enabled on the pool
Last updated on