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1.2TB 10K SAS 2.5 drives in RAID6
Hi All,
Does anyone know of any drawbacks configuring 1.2TB 10K SAS drives in RAID6 pool? I know that it is preferred to use NL-SAS for RAID6. However, what may be advantages, disadvantages for configuring 1.2TB 10K SAS drives in RAID6 pool? The array is VNX5200, the application is VMware.
Appreciate your input.
brettesinclair
715 Posts
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October 8th, 2015 00:00
Read performance will pretty much the same but write performance will be better on RAID 5.
umichklewis
1.2K Posts
1
October 6th, 2015 06:00
The primary advantage is resilience. RAID6 protects against an additional drive failure within the private RAID groups in the storage pool. The primary disadvantage is decreased write performance for RAID6, as RAID6 is better-suited to read-heavy workloads. Remember that for random writes RAID5 requires 4 back-end I/Os, versus RAID6 requiring 6 back-end I/Os. For sequential writes, RAID6's write penalty increases at a greater rate than RAID5's write pentalty, for the same number of disks.
These and other details are described in the EMC guide, EMC VNX Unified Best Practices for Performance: Applied Best Practices Guide.
Let us know if that helps!
Karl
ZaphodB
195 Posts
1
October 6th, 2015 06:00
There is certainly no technical reason why you can't use R6 with them.
Is it the rebuild times, or the overall data integrity that concerns you here, or are you thinking of making 'really big' RAID groups?
The drawback would be higher backend IOPS which would have some impact on the performance. I wouldn't expect a profound difference, but likely a measurable one.
I am using them in 8+1R5 in mixed pools; and that is within recommendations. If I wanted to make higher IOP configurations out of them I would likely use RAID groups and MetaLUNs to engage more spindles, or build pools with an appropriate structure.
brettesinclair
715 Posts
1
October 7th, 2015 01:00
One other thing to consider is the space you will "lose" to parity compared to RAID 5.
Longer rebuild times are somewhat offset by the higher rotational speeds and smaller capacities (when compared to common nl-sas drives).
For me, I still use these in R5 groups, making sure that my spares policy is adequate.
victory_is_mine
236 Posts
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October 7th, 2015 09:00
As far as performance is concerned - I will not lose anything by configuring these large drives in R5 due to higher rotational speed, will I? Just the other way around, they will perform much better than R6, won't they?
kelleg
4.5K Posts
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October 8th, 2015 13:00
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glen