Re: LVM and Postgres

Hi August. Thanks very much for your mail.

On 06/12/05, August Zajonc (augustz(at)augustz(dot)com) wrote:
> Rory Campbell-Lange wrote:
> >The server has a 250GB RAID10 (LSI 320-I + BBU) volume which I am
> >thinking of slicing up in the following way (Linux 2.6 kernel):
> >
> > / : ext3 : 47GB (root, home etc)
> > /boot : ext3 : 1GB
> > /tmp : ext2 : 2GB
> > /usr : ext3 : 4GB
> > /var : ext3 : 6GB
> > -----------------------
> > 60GB
> >
> > VG : 190GB approx
> > -----------------------
> > Initially divided so:
> > /data : ext3 : 90GB
> > /postgres : xfs : 40GB
> >
> >This gives me left over space of roughly 60GB to extend into on the
> >volume group, which I can balance between the /data and /postgres
> >logical volumes as needed.
>
> It looks like you are using fast disks and xfs for filesystem on the
> /postgresql partition. That's nice.
>
> How many disks in the array?

Four.

> One thing you miss is sticking a bunch of sequential log writes on a
> separate spindle as far as I can see with this? WAL / XFS (i think) both
> have this pattern. If you've got a fast disk and can do BBU write
> caching your WAL writes will hustle.

Yes, we don't have any spare disks unfortunately. We have enabled the
BBU write, so we are hoping for good performance. I'd be grateful for
some advice on dd/bonnie++ tests for checking this.

> Others can probably speak a bit better on any potential speedups.

I'd better test extending the Logical Volumes too!

Many thanks
Rory