Re: How to best use 32 15k.7 300GB drives?

On 1/27/11 4:11 PM, "Alan Hodgson" <ahodgson(at)simkin(dot)ca<mailto:ahodgson(at)simkin(dot)ca>> wrote:

On January 27, 2011, Robert Schnabel <schnabelr(at)missouri(dot)edu<mailto:schnabelr(at)missouri(dot)edu>> wrote:

> So my questions are 1) am I'm crazy for doing this, 2) would you change

> anything and 3) is it acceptable to put the xlog & wal (and perhaps tmp

> filespace) on a different controller than everything else? Please keep

> in mind I'm a geneticist who happens to know a little bit about

> bioinformatics and not the reverse. :-)

>

Putting the WAL on a second controller does help, if you're write-heavy.

I tried separating indexes and data once on one server and didn't really notice that it helped much. Managing the space was problematic. I would suggest putting those together on a single RAID-10 of all the 300GB drives (minus a spare). It will probably outperform separate arrays most of the time, and be much easier to manage.

If you go this route, I suggest two equally sized RAID 10's on different controllers fir index + data, with software raid-0 on top of that. RAID 10 will max out a controller after 6 to 10 drives, usually. Using the OS RAID 0 to aggregate the throughput of two controllers works great.

WAL only has to be a little bit faster than your network in most cases. I've never seen it be a bottleneck on large bulk loads if it is on its own controller with 120MB/sec write throughput. I suppose a bulk load from COPY might stress it a bit more, but CPU ends up the bottleneck in postgres once you have I/O hardware this capable.

--

A hybrid Escalade is missing the point much in the same way that having a diet soda with your extra large pepperoni pizza is missing the point.