I get this question from time to time, “How does Flex-IO compare to VMware’s View Storage Accelerator (formerly known as Content Based Read Cache)?” The answer is not one or the other it’s you should use both!
Let me explain why:
VMware View Storage Accelerator is a “Read Cache” only so it does not help with writes, it’s also limited to 2 GB of host memory. However, it does cross all images for finding common blocks to serve from RAM vs going to disk so this works well with Flex-IO.
When you combine View Storage Accelerator there are a few benefits.
- Flex-IO does not cross replica’s for common read blocks, Flex-IO common read blocks only relate to the replica and link’d clone. So, if you’re pushing out more than one pool on top of Flex-IO, View Storage Accelerator can help optimize read access replica’s taking some of the stress off Flex-IO and reducing Flex-IO CPU. From a RAM point of view removing some of the reads from Flex-IO gives more room for handling writes in the same RAM foot print, which never hurts.
- Refresh times, login times, application load times all do better with View Storage Accelerator, but when the 2 GB runs out you’re back to the speed of your disk again, this is where Flex-IO can follow up and help. Flex-IO does not have any kind of CAP for how much RAM you want to give it for Read and Write Caching.
- As I stated above, its “Read Cache” NOT Write Cache, so adding Flex-IO is going to help speed up writes as well where View Storage Accelerator by its self does not.
Side note: You can enable Content Based Read Cache at the host level and use it with any VDI platform, XenDesktop, vWorkspace, etc.
I hope this helps to understand that you should be using Flex-IO and View Storage Accelerator together.