We are planning to buy two servers which will going to host an SQL database(PostgreSQL). The second server will work as a live replication of the first database server (hot standby). The question I'm having is about the RAID level to chose for the servers.

Initially I was planning to use RAID 10 on both servers from performance point of view, but since we plan to store 20-30Tb of data during 5 years, RAID 10 gets a bit too expensive (especially since we have to buy two machines). And also I was thinking that the redundancy of RAID 10 is not really needed if we have replication anyway.

So now I'm considering having RAID 5 on each of the replicating servers. With this setup even if there is a failure of RAID 5 on one machine, accompanied by another failure during the rebuild I'll still have a working DB machine. My guess is that the system should be quite reliable this way. Do you think that's a reasonable decision ?

PS I don't really want to use RAID6, because of the write penalty of it.


I think as long as you're truly replicating all the data and services from one machine to the other, R5 will be just fine unless you hit a performance bottleneck. Just be sure to designate a hot spare.

I would point out though, that when you get to the quantities you're talking about the rebuild speed of a R5 array could get... lengthy, depending on the number of spindles and the load on your controller.

| improve this answer | |
  • Also RAID5 for database has same performance as single HDD. And it does not scale with number of drives. – DukeLion May 21 '12 at 5:15
  • Who told you that? – SpacemanSpiff May 21 '12 at 12:14
  • I've seen a lot of benchmarks and did some tests myself. IOPS performance of RAID5 array is almost the same to single drive. – DukeLion May 21 '12 at 12:28
  • 1
    There are way too many factors to make that broad a statement, imho. – SpacemanSpiff May 21 '12 at 13:02
  • Ok, may be my English is too bad to express it correctly. I'm speaking about RAID configuration, assuming all other factors: controller cache, disk type and condition, filesystem settings are identical – DukeLion May 21 '12 at 13:08

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.