Use this procedure to determine if you need a first write log device for your 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 OS8.7.0.
To determine if you need to add more than one write log device, see When to Add More Write Log Devices (BUI).
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