It would be insane to hook up 12 drives in a RAID5. If you lose a drive, it's gonna take a day to rebuild the array and what happens if you lose a second drive while you're rebuilding? 4 x 250GB drives in RAID 5 took about 10 hours to rebuild. It is probably quicker to format and re-install. I hope you have backups. I use RAID 1+0 for database servers. For a app, file, or mail server, I do RAID 1 unless I needed the space, then I'd do RAID 6. I don't run RAID 5 on any of my servers anymore because I need redundancy beyond losing 1 drive and the write performance blows. I should note that you can get sufficient performance from a RAID 5/6 by using a controller with 256MB of cache and allocated most of it to write-back cache. Also, you should have a lot of RAM to cache database pages in RAM and cache queries to avoid hitting the disk. -Chris Bret Baptist wrote: > On Wednesday 28 May 2008 1:47:32 pm Josh Paetzel wrote: > >> On Wednesday 28 May 2008 11:14:50 am Justin Krejci wrote: >> >>> http://download.intel.com/support/motherboards/server/srcsas18e/sb/axxrpc >>> m2 _ tps_10.pdf >>> >>> Benefits are identified in this PDF. >>> Data caching (write-back cache can greatly improve write performance) >>> >>> Busy databases servers commonly need lots of I/O >>> >>> Also consider running RAID10 if you have drive availability (4 drive >>> minimum) as you will get much higher I/O performance with that as well >>> especially with writes. Though if you need the capacity, RAID5 will give >>> you one drive more of capacity. RAID10 can also give you a smaller chance >>> of data loss due to drive failures as you can potentially lose up to half >>> of your drives and still operate whereas using RAID5 and losing 2+ drives >>> = disaster. >>> >> Somewhere a DBA just rolled over in his grave at the mention of a database >> using RAID 5. If you're ever going to care about performance at all don't >> use RAID 5. It's particularly slow at the sorts of write I/O database >> systems typically generate. >> > > For the most part this is true, however on a lot of modern RAID controllers if > you hook 12 drives up in RAID-5 you are going to see amazing performance. > > Here is an article with a very thorough review of 9 SATA RAID cards: > http://tweakers.net/reviews/557/26/comparison-of-nine-serial-ata-raid-5-adapters-pagina-25.html > The issue here is that they do not do a RAID-10 test with 12 drives. > > I don't know what they are doing on the Coraid SR 1521 to make RAID-5 faster > than RAID-10, but when you get up to 14 drives in the chassis you get much > better throughput, now mind you this is not random I/O, just another thing to > think about: > http://coraid.com/support/sr/ANSR002.pdf > > For a large number of drives in a RAID-5 you get really good performance and > much higher capacity. > > Not that this is really relevant to the original poster. > > > Thanks. > -------------- next part -------------- An HTML attachment was scrubbed... URL: http://mailman.mn-linux.org/pipermail/tclug-list/attachments/20080528/89ac9d28/attachment.htm