vSphere vFlash read cache (VFRC) Deprecation Announced
Recently someone asked me about VFRC. I have played around with it a little bit in the past, however I decided to do a little bit of research around it. While researching VFRC I learned that it was, at that time going to be deprecated which it now will be with the next major release of vSphere. VFRC looks to be supported in 6.0 6.5 and 6.7 still.
VFRC was introduced in 5.5 and allowed us to pool multiple flash drives, which would enhance performance of IO workloads using local cache media for read IO.
A few lessons I learned while trying to find more info:
- Sizing: It was recommended to start with 10% of your VMDK size for your cache size and work from there.
- Monitor all your applications to see what your needs are, every environment is different
- Match your block size, in order to get this info use vscsistats, which will give you the most commonly used block size
- Maximum size is 400 GB however you may run into an issue where you can only enter 200 GB, resolve this in advanced settings VFLASH.MaxCacheFileSizeMB and change the value to 409600
- Flash cache metrics are in the advanced section under disk counter or with “esxcli storage vflash cache stats get -c <name of cache>”
- You need a minimum hardware version of 10 to enable Flash cache, the option is not available if you are below this version
- Not Compatible with VSAN
Feedback I received was that there was a noticeable improvement in performance after enabling VFRC . It will be sad to see it go, nevertheless with the small amount of customers using it I can see why VMware would start to phase it out. I believe the focus today will be on VSAN which also has a form of flash cache.