VMware Flash Read Cache Installation

31st March 2015 0 By Simon

In my home lab I decided to install 3 SanDisk SDSSDP-128G-G25 SSD’s for VMware’s Flash Read Cache, this lets you accelerate virtual machine performance through the use of host resident flash devices as a read cache. Now please understand that these drives aren’t on the HCL so your mileage may vary.

I have a full page dedicated to Flash Read Cache being prepared for my VCAP 5.5 Guide so I won’t do the whole thing here.

Finally this post was initially created using vSphere 5.5 but the steps are identical when completing the work on a vSphere 6 environment.

SanDisk SSDConfiguring Virtual Flash Resources

As this was a new feature in vSphere 5.5 you’re going to need to use the vSphere Web Client for this work.

You can do this on a per host basis following the below instructions.


In the vSphere Web Client, navigate to the host, click the Manage tab and click Settings


Under Virtual Flash, select Virtual Flash Resource Management and click Add Capacity


From the list of available SSDs, select the drives you want to use for virtual flash and click OK


The virtual flash resource is created. You can add up to 8 devices to the cache.

If you have added SSD’s to multiple hosts, rather than add the devices individually you can add them all from one screen.

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At the cluster level, right click the cluster, choose All vCenter Actions and then Add Virtual Flash Resource Capacity


Click the hosts you want to configure and click OK

Configure Flash Read Cache for a VM

To configure Flash Read Cache for a VM first you need to remember that this is assigned per disk.


Using the Web Client open the settings for the VM and expand the hard disk, you can see that currently I don’t have anything configured in the read cache.

VMware recommend “Ideally the cache would be large enough to hold the active working set, but not much larger. Configuring a larger-than-necessary cache can reduce performance by making that flash space unavailable for other vFRC-enabled virtual machines or for host swap cache.

Configure vFRC for all required drives and click OK.

That’s it, vFRC has been installed and configured. Fairly easy to do but has the potential to increase performance on your infrastructure with a fairly cheap upgrade to each host.