Re: BBU Cache vs. spindles

Ben Chobot wrote:
> On Oct 7, 2010, at 4:38 PM, Steve Crawford wrote:
>
> > I'm weighing options for a new server. In addition to PostgreSQL, this machine will handle some modest Samba and
Rsyncload. 
> >
> > I will have enough RAM so the virtually all disk-read activity will be cached. The average PostgreSQL read activity
willbe modest - a mix of single-record and fairly large (reporting) result-sets. Writes will be modest as well but will
comein brief (1-5 second) bursts of individual inserts. The rate of insert requests will hit 100-200/second for those
briefbursts. 
> >
> > So...
> >
> > Am I likely to be better off putting $$$ toward battery-backup on the RAID or toward adding a second RAID-set and
splittingoff the WAL traffic? Or something else? 
>
> A BBU is, what, $100 or so? Adding one seems a no-brainer to me.
> Dedicated WAL spindles are nice and all, but they're still spinning
> media. Raid card cache is waaaay faster, and while it's best at bursty
> writes, it sounds like bursty writes are precisely what you have.

Totally agree!

--
  Bruce Momjian  <bruce@momjian.us>        http://momjian.us
  EnterpriseDB                             http://enterprisedb.com

  + It's impossible for everything to be true. +