Re: Hardware performance

I've got a Dell 2650 set up with 5 drives and a separate app server connecting with JDBC. Since you've only got 5 drives, my conclusion regarding the best balance of performance and redundancy was:

2 drives have the OS, swap, and WAL in RAID-1
3 drives have the data in RAID-5

If you can afford it, get the 2+3 split backplane and make the 3 data drives the biggest, fastest you can afford. Currently that means the 15k 73GB drives, which would give you 146GB for data. Make the OS drives smaller and slower if you need to save cash.

If only it had six drive bays....you could use 4 drives for the data and do RAID-10. If you've got the additional rackspace available, you could get the 5U Dell 2600 instead for the same ballpark cost. If you order it with rack rails, it comes all set up for rack installation...a special sideways faceplate and everything.

By the way, RAID-5 is not the best fault tolerance, RAID-1 or RAID-10 is. And you can certainly hot-swap RAID-10 arrays. I've actually done it....recently! I am of the mind that single drives are not an option for production servers - I just don't need the pain of the server going down at all. Although they DO go down despite redundancy...I just had a SCSI backplane go out in a Dell 6600 that has every bit of redundancy you can order. While uncommon, the backplane is one one of the many single points of failure!

Roman Fail
POS Portal, Inc.

-----Original Message-----
From: Balazs Wellisch [mailto:balazs(at)neusolutions(dot)com]
Sent: Wed 7/16/2003 7:57 PM
To: pgsql-performance(at)postgresql(dot)org
Cc:
Subject: [PERFORM] Hardware performance


Hi all,

first of all I'd like to thank everyone who responded to my earlier post. I have a much better understanding of postgres performance tuning now. In case anyone's interested we've decided to go with RH9 and PostgreSQL 7.3 and we'll do the OS and DB tuning ourselves. (should be a good learning experience)

We are now getting ready to purchase the hardware that will be used to run the database server. We're spending quite a bit of money on it because this will eventually, if things go well within two months, become a production server. We're getting all RH certified hardware from Dell. (Dell 2650)

We're now stuck on the question of what type of RAID configuration to use for this server. RAID 5 offers the best fault tolerance but doesn't perform all that well. RAID 10 offers much better performance, but no hot swap. Or should we not use RAID at all. I know that ideally the log (WAL) files should reside on a separate disk from the rest of the DB. Should we use 4 separate drives instead? One for the OS, one for data, one for WAL, one for swap? Or RAID 10 for everything plus 1 drive for WAL? Or RAID 5 for everything?

We have the budget for 5 drives. Does anyone have any real world experience with what hard drive configuration works best for postgres? This is going to be a dedicated DB server. There are going to be a large number of transactions being written to the database. (Information is logged from a separate app through ODBC to postgres) And there will be some moderately complex queries run concurrently to present this information in the form of various reports on the web. (The app server is a separate machine and will connect to the DB through JDBC to create the HTML reports)

Any thoughts, ideas, comments would be appreciated.

Thank you,

Balazs Wellisch
Neu Solutions
balazs(at)neusolutions(dot)com