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4362
Pool Drive Failure
Unity 500F Storage Array.
Pool1 12+1 (14 SSD disks drives).
Can I lose more than one disk drive at the same time in the Pool without losing any data?
This post is more than 5 years old
47 Posts
0
4362
Unity 500F Storage Array.
Pool1 12+1 (14 SSD disks drives).
Can I lose more than one disk drive at the same time in the Pool without losing any data?
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Anonymous
5 Practitioner
5 Practitioner
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274.2K Posts
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August 1st, 2017 18:00
Hi RMC,
With a RAID 5 RAID level in this case the answer would be no. You would have data loss or unavailability. This is because of the Dynamic pool architecture; there would be certain extents that would rely on those two drives to where you would lose an entire RAID set. This could effectively take the entire pool down as well.
Thanks
rmc_dell
47 Posts
0
August 1st, 2017 13:00
The Pool is a Dynamic Pool.
paranoidandroi1
20 Posts
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August 2nd, 2017 00:00
Hi,
That would also be true for traditionnal pools.
For both pool types, probability is higher with 12+1 than 4+1. But two drives of the same raid set means DU, or worst DL if disks wont spin up again.
For dynamic pools, if the a RAID5 4+1 choice means a DU when 2 disks amongst 200 (for example) fail at the same time, that is a risky option.
EnriquePereira
6 Posts
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August 29th, 2017 01:00
I have experience with VNX, and always prefer to use raid 4+1 in traditional pools. A pool with 20 disks would have 4 internal raids, so it could be possible to loose more than one drive as loong as they belong to different raid group.
But now I am planning to by a 450F with 20 1,6TB ssd, and I am not sure what configuration select:
- 1 dynamic pool with 20 disks (23,5 TB)
- 2 dynamic pools with 10 disks (21,7TB)
I am worried about the fact of loosing more than one drive at the same time.
Rainer_EMC
8.6K Posts
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September 1st, 2017 06:00
a LUN isnt restricted to one raidgroup
if you want to be protected against dual drive failue than you should use RAID6
EnriquePereira
6 Posts
0
September 1st, 2017 08:00
The problem for raid6 will be the performance. It is not recommended.
That is the reason for me to consider 2 different pools.
The question is that if I create a traditional pool with 20 disks, I can choose raid5 4+1 and could (potentially) tolerate 4 failed disks. With dynamic pool, it internally create one isolation domain every 64 disks, so for me it seems more probable 2 failures in 64 disks thant 2 failures in 5 disks.
I suppose that EMC should have a good explanation for doing this, but I cannot find it. Even xtreamio uses somethink like raid 6.