How to add ZIL write and L2ARC read cache SSD devices in FreeNAS

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FreeNAS, a popular open-source network-attached storage (NAS) operating system, supports the use of solid-state drives (SSDs) as a write cache (ZIL) and read cache (L2ARC) to improve performance. Here’s how to add ZIL and L2ARC SSD devices in FreeNAS:

  1. Connect the SSD devices to your FreeNAS system and ensure that they are recognized in the Storage > Disks menu.
  2. Go to the Storage > Volumes menu and select the volume for which you want to add the SSD cache.
  3. Click the Edit button and go to the Volume Settings tab.
  4. Under the Cache section, select the checkbox for “Use cache disk” and choose the ZIL SSD from the drop-down menu. This will configure the SSD as a write cache.
  5. If you also want to add a read cache, select the checkbox for “Use L2ARC” and choose the L2ARC SSD from the drop-down menu.
  6. Click the Save button to apply the changes.
  7. To verify that the cache drives are in use, you can go to the System > Tunables menu and look for the vfs.zfs.cache.size and vfs.zfs.l2arc.headroom tunables. The values should reflect the amount of cache that is being used by the system.

Note: Before adding cache drives, it’s recommended to backup important data as adding cache drives can cause data loss in the event of hardware failure. Additionally, it’s a good idea to verify that the SSDs are compatible with your FreeNAS system and have adequate capacity for your needs.

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