When to Add More Disks (CLI)
Use this procedure to determine if you need to add more disks. Note that disks can be over-utilized by making a poor choice for the RAID profile and/or ZFS record size. In this case, it might be possible to reduce existing disk utilization by moving from RAIDZ to mirrored profiles, and/or matching ZFS record sizes to client I/O sizes.
In addition, if the system is configured with no read- or write-optimized flash drives, then all of the I/O operations beyond DRAM are served by disks. For better performance, consider using flash for any workload that includes random reads or synchronous writes.