Re: mirroring data on different drives?

Steve <steve(at)nospam(dot)postgresql(dot)org> wrote:
> Someone please please help me!!!! :-(
>
> Steve
>
> Steve wrote:
> > Hi,
> >
> > I've been running postgres on my server for over a year now and the
> > tables have become huge. I have 3 tables that have data over 10GB each
> > and these tables are read very very frequently. In fact, heavy searches
> > on these tables are expected every 2 to 3 minutes. This unfortunately
> > gives a very poor response time to the end user and so I'm looking at
> > other alternatives now.
> >
> > Currently, the postgresql installation is on a single disk and so all
> > the tables have their data read from a single disk. Searching on
> > different tables by multiple users at the same time results in very slow
> > searches, as it's mainly dependant on the spindle speed. I recently
> > gained access to another server which has 3 SCSI disks. I know there is
> > a way to mirror the tables across the three different disks but I'm not
> > sure if it's as easy as symlinking the files (WAL files only?) across.
> > Can anyone please tell me what to do here and how to harness the power
> > of the three SCSI drives that I have. Which files in the data directory
> > need to be moved? Is this safe? Can backups etc be easily done? Any
> > information will be greatly appreciated. Thank you,

The answer to your question is OS/hardware dependent.

The best alternative is to have hardware-based RAID with battery backing.
This provides excellent speed with good safety.

The next option is to use some sort of software RAID. How to do this depends
on the OS you are using, and will be covered in the docs for that OS.

I don't think a lot of symlinking is a very good way to distribute your data.
Many folks have had success by keeping the data and the WAL on seperate disks,
but that leaves you with a third disk that isn't helping any.

--
Bill Moran
Potential Technologies
http://www.potentialtech.com