Re: BBU Cache vs. spindles

On Wed, 2010-10-20 at 22:13 -0400, Bruce Momjian wrote:
> 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
activitywill be modest - a mix of single-record and fairly large (reporting) result-sets. Writes will be modest as well
butwill come in brief (1-5 second) bursts of individual inserts. The rate of insert requests will hit 100-200/second
forthose brief bursts. 
> > >
> > > 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!

BBU first, more spindles second.

>
> --
>   Bruce Momjian  <bruce@momjian.us>        http://momjian.us
>   EnterpriseDB                             http://enterprisedb.com
>
>   + It's impossible for everything to be true. +
>

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