When to Add the First Write Log Device (BUI)

Use this procedure to determine if you need a first write log device for Oracle ZFS Storage Appliance. Fibre Channel and iSCSI writes are synchronous and benefit from log devices when the write cache is enabled. Be sure to thoroughly read and understand the documented implications of enabling write caching on LUNs before proceeding. For more information, see Space Management for Shares in Oracle ZFS Storage Appliance Administration Guide, Release OS8.8.x.

To determine if you need to add more than one write log device, see When to Add More Write Log Devices (BUI).

  1. Create a worksheet as described in Creating a Worksheet (BUI).
  2. Click the add icon icon indicating an item can be added next to Add statistic.
  3. Go to PROTOCOL: NFSv2 operations: Broken down by type of operation.
  4. Repeat steps 2 and 3 for each protocol that is configured for your appliance.
  5. Wait at least 15 minutes.


    Fifteen minutes is a general guideline. This amount of time may be adjusted if you have a performance-sensitive, short-duration synchronous write workload.
  6. Examine the graph(s).

    Consider adding a write log device when one or all of the following conditions are present:

    • The sum of iSCSI writes, Fibre Channel writes, and NFS/SMB synchronous operations is at least 1000 per second

    • There are at least 100 NFS commits per second