After deploying a Proliant ML150 G6 with ESXi 5.5U2 to a remote office, the users were complaining of dismal performance. After investigating and reviewing various metrics of the machine, we noticed very high disk latencies (average of 20ms).
After doing some “Googleing”, it was decided to install the Battery-Backed-Write-Cache battery module (what a mouthful!). Yes, one would think that once you install and configure a RAID controller, that would be it, but not in this case.
Nonetheless, a battery was procured and plugged in. The BIOS upon boot immediately states to use the HP Array Configuration Utility to enable the read/write cache. One needs to install the HP utilities onto the ESXi box if it wasn’t built from the HP ESXi ISO. By logging into the console via SSH, first confirm the battery status and then enable the read/write cache ratio. In our instance we configured 50% read / 50% write. Refer to this post for the HP ACU commands.
Check out the performance gain / decreased latency: