Hi all,

I have question about what configuration folks have used for RAID on
their servers. We bought a Dell 2950 Poweredge with 2 Intel Xeon 5150
Dual Core processors and 4GB of memory. We have 6 146GB, 15k RPM SAS
disks. OS will be RHEL 4AS and we have PERC 5/i as our RAID controller.
The question is; what is the optimal RAID config for the webserver using
Postgres as a database? Your experiences, positive and negatives would
be appreciated.

Thanks,
Patrick

--
Patrick A. Smith Assistant System Administrator
Ocean Circulation Group – USF - College of Marine Science
http://ocgweb.marine.usf.edu Phone: 727 553-3334

The trouble with doing something right the first time is that nobody
appreciates how difficult it was. - La Rochefoucauld

On Fri, 31 Aug 2007 09:35:57 -0400, Patrick wrote:

> Hi all,
>
> I have question about what configuration folks have used for RAID on
> their servers. We bought a Dell 2950 Poweredge with 2 Intel Xeon 5150
> Dual Core processors and 4GB of memory. We have 6 146GB, 15k RPM SAS
> disks. OS will be RHEL 4AS and we have PERC 5/i as our RAID controller.
> The question is; what is the optimal RAID config for the webserver using
> Postgres as a database? Your experiences, positive and negatives would
> be appreciated.

You would probably get a better answer in a PostgreSQL user group. In
general, most databases would recommend:

4 Drives - RAID 5 for OS and Data Files
2 DRIVES - RAID 1 Mirroring for Transaction/Write Ahead Logs

Using this configuration, the write-ahead logs are written sequentially.
If you drop your whole RAID 5 array, you can restore from backup, and
apply the transaction logs to bring your data up to the moment of loss.

Don't think it's impossible to lose an entire Array. I've seen it happen,
particularly with DELL controllers.




--
George Sexton
MH Software, Inc. - Home of Connect Daily Web Calendar
http://www.mhsoftware.com/connectdaily.htm

Patrick wrote:

> Hi all,
>
> I have question about what configuration folks have used for RAID on
> their servers. We bought a Dell 2950 Poweredge with 2 Intel Xeon 5150
> Dual Core processors and 4GB of memory. We have 6 146GB, 15k RPM SAS
> disks. OS will be RHEL 4AS and we have PERC 5/i as our RAID controller.
> The question is; what is the optimal RAID config for the webserver using
> Postgres as a database? Your experiences, positive and negatives would
> be appreciated.
>
> Thanks,
> Patrick
>


It depends how much disk space you actually need.

For fastest reads RAID 1+0 would probably be best. Stripe the data across 2
disks and mirror each twice. You would only have 292GB of space but read
speeds would be almost 6 x single disk reads.

With those disks you'd get a sustained 350MB/s unbuffered reads.


--
Brian Wakem