When to Add More Disks (BUI)

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.

  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 DISK: Disks: Broken down by percent utilization.
  4. Right-click on 70% range average and click By disk.
  5. Wait at least 30 minutes.


    Thirty minutes is a general guideline. If you have short-duration workloads that are bottlenecked on disk utilization, you may want to consider selecting additional disks at less than 30 minutes.
  6. Examine the graphs.

    You might want to use more disks when at least 50% of existing disks are at least 70% utilized.