When you have an Isilon cluster when is the best time to add SSD capacity and will the system enhance the performance?

Many clusters can take advantage of SSD's within some or all of the nodes, SSD's can be used in a few different ways determining if I need more can be fairly simple.

SSD's can be used as

1) To hold live data

2) To hold metadata on a specific pool

3) To enable global namespace acceleration - ie help accelerate metadata cluster wide especially on nodes without SSD's (like NL nodes)

If your applications accessing the cluster and create larger amounts of directories with lot's of small files your system will typically be doing lot's of file metadata operations.   If you application always knows the file path for access and has fewer larger files then metadata lookups to the cluster will typically be much less.

The easiest way to determine how busy the system is doing metadata lookups is to leverage InsightIQ.  Don't have InsightIQ you can get a trial license and install the software inside a VM instance.

The report to review is located under Performance Reporting, Client Performance, Select the Protocol Operations rate and Protocol Operations latency.  If you see high values for namespace reads and namespace writes you should add SSD's to the environment for better overall performance.

In this case my sample IIQ report shows most of the demo cluster workload is writes,  expect different numbers on your production cluster.