How helpful is FAST Cache on my array?

If you've recently installed a new system with FAST Cache and you're trying to determine how much work that it's helping out with it can be confusing to determine if it's been worthwhile.

You can do a couple of things

1) collect nar files over a few days and have your EMC SE review the outputs and provide a report

2) Leverage a tool such as VNX Monitoring and Reporting and view the ongoing reports that can be generated.

VNX monitoring and reporting is a software license which is based on the frame type you have installed.  It supports NAS and SAN workloads for CX4, NS and VNX systems so even if you have older arrays it can provide some value to your environment.  You can license up to 5 storage arrays onto a singe M&R server.

Don't have the license but want to try it?  You can download a trial version @  You need an EMC Support login id.

https://download.emc.com/downloads/DL43275_VNX-Monitoring-and-Reporting-Windows-Setup-File-1.01.exe

Once you have it installed and collecting data from your array you can review the relevant reports.  The one that I find the most useful in the initial stages can be found in the following path.

VNX  > Details > VNX Block All Reports > VNX Block Arrays Summary > List of Arrays > "Select your Array name"  >> Fast Cache > Array vs FAST Cache IOPS

You can also search for the desired report in the search bar in the top right of the website.

You should see a chart similar to the attached screenshot.

In this case the FAST Cache is doing roughly half the IOPS on the storage array. You can customize the reporting period so you can look at one day or longer periods.