RAID-5 and database servers

Jefferson Ogata poweredge at antibozo.net
Thu Mar 11 12:22:15 CST 2010


On 2010-03-11 18:09, Preston Hagar wrote:
> Actually it says if money is no object, go with RAID 10:
> 
> http://www.orafaq.com/wiki/RAID#RAID_10
> 
> RAID 10 is the ideal RAID level in terms of performance and
> availability, but it can be expensive as it requires at least twice
> the amount of disk space. If money is no objective, always choose RAID
> 10!
> 
> I would agree with the RAID 10 recommendation.  I at one time did a
> lot of RAID 5 to try to comprimise price vs performance, but had
> several array failures resulting in having to restore from backup.
> Now, I put anything important on either RAID 1, or RAID 10.  Basically
> I use RAID 1 if it needs to be reliable and RAID 10 if it needs to be
> reliable and fast.

I've got several hundred disks running on RAID 5 and I've had one actual 
full RAID failure in 10 years, and that was my fault.

In terms of performance, depending on the workload, RAID 5 can 
outperform RAID 10. Furthermore Oracle's recommendations are based on 
what appears to be 5-10-year-old data, back when mid-level RAID 
controllers weren't capable of pushing ~700 MB/s onto a RAID 5. 
Nowadays, they can do that, and achieve pretty stellar IOPS as well. The 
difference in performance between RAID 5 (or better yet, RAID 50, 
striped using LVM), and RAID 10 is not what it used to be. Bear in mind 
also that now that Oracle is a hardware company, they'd just love you to 
buy almost twice as much disk (from them).

*Again*, this is why if you have particular performance requirements, 
you should consult with your database vendor to determine what bandwidth 
and IOPS you need, and benchmark your gear using different RAID configs. 
You may find that RAID 5 is just fine performance-wise, and you can get 
around 1.7 times the storage capacity with the same rack space, heat, 
and power load over RAID 10. Asking here you're just going to get people 
parroting Oracle's stale recommendations and speculating wildly without 
knowing anything about your workload.



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