Re: Deploying PostgreSQL on CentOS with SSD and Hardware RAID

On 5/11/2013 3:10 AM, Matt Brock wrote:
> On 10 May 2013, at 16:25, David Boreham <david_list(at)boreham(dot)org> wrote:
>
>> I've never looked at SLC drives in the past few years and don't know anyone who uses them these days.
> Because SLCs are still more expensive? Because MLCs are now almost as good as SLCs for performance/endurance?

Not quite. More like : a) I don't know where to buy SLC drives in 2013
(all the drives for example for sale on newegg.com are MLC) and b)
today's MLC drives are quite good enough for me (and I'd venture to say
any database-related purpose).

>
> I should point out that this database will be the backend for a high-transaction gaming site with very heavy database usage including a lot of writes. Disk IO on the database server has always been our bottleneck so far.

Sure, same here. I wouldn't be replying if all I did was run an SSD
drive in my laptop ;)

>
> Also, the database is kept comparatively very small - about 25 GB currently, and it will grow to perhaps 50 GB this year as a result of new content and traffic coming in.

Our clustering partitions the user population between servers such that
each server has a database about the same size as yours. We tend to use
200 or 300G drives on each box, allowing plenty space for the DB, a copy
of another server's DB, and log files.

>
> I've asked our HP dealer for this information since unfortunately it doesn't appear to be available on the HP website - hopefully it will be forthcoming at some point.
>

This is a bit of a red flag for me. During the qualification process for
our SSD drives we: read the technical papers from Intel; ran lab tests
where we saturated a drive with writes for weeks, checking the write
endurance SMART data and operation latency; modified smartools so it
could read all the useful drive counters, and also reset the wear
estimation counters; performed power cable pull tests; read everything
posted on this list by people who had done serious testing in addition
to the tests we ran in house. I'm not sure I'd want to deploy "Joe
Random SSD du jour" that HP decided to ship me. You might consider
buying boxes sans drives and fitting your own, of a known trusted type.