Flash Read Cache

[joeflint2]

Hi, we're moving to ESXi v5.5, and currently have mostly IBM HS22/23 blade servers.

I'd like to understand what Flash Read Casch is and how to use. When reviewing current documentation I cannot understand what it is and for what hardware it applies. Can anyone explain simply frowhat type of hardware it applies and the benefits (without URL to docs)

Thanks

[JPM300 · Accepted solution]

The long and short of it is Vmware is putting another piece into the hypervisor that buffers I/O requests from your VM's into fast SSD disks or flash cards to speed up reads/writes to your SAN.  An easy way to think of this is if you have ever setup a Disk-to-Disk-to-Tape setup.  You dump everything to Disk first for speed(Multiple jobs at once, faster write times, ect, ect), then send everything to tape.  Its kind of the same idea with Flash Read Cache.  the VMDK's I/O is buffered or sent to the flash cache, then sent to the SAN to increase performance.

Page 6 on this wmare pdf has a good diagram of it:

http://www.vmware.com/files/pdf/vSphere_55_Flash_Read_Cache_Whats_New_WP.pdf

Hope this helps