Re: Deploying PostgreSQL on CentOS with SSD and Hardware RAID

On Fri, May 10, 2013 at 11:34 AM, Evan D. Hoffman
<evandhoffman(at)gmail(dot)com> wrote:
> I'd expect to use a RAID controller with either BBU or NVRAM cache to handle
> that, and that the server itself would be on UPS for a production DB. That
> said, a standby replica DB on conventional disk is definitely a good idea in
> any case.

Sadly, NVRAM cache doesn't help (unless the raid controller is
managing drive writes down to the flash level and no such products
exist that I am aware of). The problem is that provide guarantees the
raid controller still needs to be able to tell the device to flush
down to physical storage. While flash drives can be configured to do
that (basically write-through mode), it's pretty silly to do so as it
will ruin performance and quickly destroy the drive.

Trusting UPS is up to you, but if your ups does, someone knocks the
power cable, etc you have data loss. With on-drive capacitor you only
get data loss via physical damage or corruption on the drive.

merlin