Re: RAID0 and pg_xlog

On Fri, Sep 09, 2005 at 09:43:56AM -0500, Scott Marlowe wrote:
> On Wed, 2005-09-07 at 16:15, Jim C. Nasby wrote:
> > On Wed, Sep 07, 2005 at 01:02:18PM -0500, Scott Marlowe wrote:
> > > On Wed, 2005-09-07 at 12:40, Jim C. Nasby wrote:
> > > > On Wed, Sep 07, 2005 at 12:47:43PM -0700, Qingqing Zhuo wrote:
> > > > > Xlog will be the only believable data if your system crashed. So it is a dangerous practice to put xlog stuff in RAID0.
> > > >
> > > > No more or less so than putting your main database on RAID0. If any
> > > > drive fails, you lose everything.
> > >
> > > Sounds like a good place to have replication.
> >
> > If you used syncronous replication, maybe. Otherwise failure of any
> > drive means you just lost data. And remember that the more drives you
> > have in your array the more likely you'll have a failure in a given
> > time period.
> >
> > Basically, if you can afford to setup replication on 2 machines with
> > RAID0 you can afford to setup RAID10 on one machine, which will usually
> > be a better bet.
>
> Yeah, I was thinking pgpool here.

pgpool is a connection pool; it has (almost) nothing to do with
replication. It certainly doesn't work to provide any kind of data
security on a RAID0 setup.

I'm not arguing against anything people have suggested, only pointing
out that if you're using RAID0 your data is not safe against a drive
failure, except possible using pgcluster (some would argue that
statement-based replication isn't as reliable as log-based).
--
Jim C. Nasby, Sr. Engineering Consultant jnasby(at)pervasive(dot)com
Pervasive Software http://pervasive.com work: 512-231-6117
vcard: http://jim.nasby.net/pervasive.vcf cell: 512-569-9461