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.
Currentlythat means the 15k 73GB drives, which would give you 146GB for data.  Make the OS drives smaller and slower if
youneed 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
rackspaceavailable, 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
justhad a SCSI backplane go out in a Dell 6600 that has every bit of redundancy you can order.  While uncommon, the
backplaneis one one of the many single points of failure!  
 
 
Roman Fail
POS Portal, Inc.
 
 

    -----Original Message----- 
    From: Balazs Wellisch [mailto:balazs@neusolutions.com] 
    Sent: Wed 7/16/2003 7:57 PM 
    To: pgsql-performance@postgresql.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
postgresperformance tuning now. In case anyone's interested we've decided to go with RH9 and PostgreSQL 7.3 and we'll
dothe 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
quitea 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
faulttolerance but doesn't perform all that well. RAID 10 offers much better performance, but no hot swap. Or should we
notuse RAID at all. I know that ideally the log (WAL) files should reside on a separate disk from the rest of the DB.
Shouldwe use 4 separate drives instead? One for the OS, one for data, one for WAL, one for swap? Or RAID 10 for
everythingplus 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
worksbest for postgres? This is going to be a dedicated DB server. There are going to be a large number of transactions
beingwritten to the database. (Information is logged from a separate app through ODBC to postgres) And there will be
somemoderately complex queries run concurrently to present this information in the form of various reports on the web.
(Theapp 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@neusolutions.com