Re: Deploying PostgreSQL on CentOS with SSD and Hardware RAID

On 05/10/2013 12:46 PM, Merlin Moncure wrote:
> On Fri, May 10, 2013 at 11:34 AM, Evan D. Hoffman
> <evandhoffman@gmail.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
>
Well we have dual redundant power supplies on separate UPS so could something go wrong yes, but a tornado could
come along and destroy the building also.


--
Stephen Clark
*NetWolves*
Director of Technology
Phone: 813-579-3200
Fax: 813-882-0209
Email: steve.clark@netwolves.com
http://www.netwolves.com