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NickJW1978
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September 9th, 2009 13:00
RAID 6 or RAID 10 for the NX3000?
I know this unit comes as just RAID 5 standard but we were looking to possibly change this to a RAID 6 or RAID 10. Can you provide any benchmarks with regards to disk throughput and rebuild times for the two? I know that RAID 6 will have a longer rebuild time due to the parity rebuild, but the ability to survive two drive failures is a plus, as if a second drive dies during the rebuild we're still OK. And, we can't have a hot spare with RAID 10 (no extra slots), so the rebuild time is a need to know.
NickJW1978
2 Posts
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Posted September 10th, 2009 10:00
Is there a rule of thumb in general on rebulid times between a RAID 6 versus RAID 10? For instance, if I had a 1TB of raw data on 4 x 250GB drives (in a RAID 6 and RAID 10) and there is a drive failure with the RAID 10 be 2x faster or 3x faster say then the RAID 6 in rebuild time?
Andreas Erson
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Posted September 10th, 2009 02:00
I'm afraid I can give any specific answers about disk throughput and rebuild times. But those who can would certainly want to know more details about your harddrives - SAS or SATA, harddrive size and number of drives.
Generally I can tell you this about the different raid configurations.
Rebuild times:
* Raid 10 will be faster than Raid 5 since you don't have to re-create data from parity.
* Raid 6 generally has a slower rebuild than Raid 5 due to the double parity.
Throughput:
* Raid 10 should perform better than Raid 5 in most scenarios (heady sequential reads could be one scenario where Raid 5 would be better than Raid 10).
* Raid 5 performs better than Raid 6 when writing due to the double distributed parity of Raid 6. When reading performance should be similiar.
Throughput during rebuild:
* In Raid 10 a rebuild is only affecting the particular Raid 1 set where the rebuild is taking place. Throughput during the rebuild is thus pretty good, at least with larger arrays.
* In Raid 5 the performance is pretty dysmal during a rebuild and even worse on Raid 6 because of the double parity.
Other considerations:
* Raid 10 can only safely handle one drive failure. If two drives fails and they are part of the same Raid 1 set the entire array has failed. In a best case scenario you can loose as many drives as there are Raid 1 sets in the Raid 10.
* If you use Raid 5 you should definately have a hot spare.
* If you only have one array it's always better to have a Raid 6 than a Raid 5 with a hotspare. That is if the performance of a Raid 6 array is acceptable.