RAID Disk failure - one per day (3ware 9650SE

There are several factors here.

These are very big drives. There's a good reason it's generally recommended not to use RAID5 (or other parity RAIDs) with extremely large arrays: they take a long time to rebuild. The rebuild process puts a lot more stress on all remaining drives than usual, leaving a very high chance to trigger another failure. RAID 6 is better than 5, but it can still have issues as you see here.
These drives are probably from the same batch. Normally it's recommended to get drives from different batches, or even different ages, to stagger likely failures as they occur.
These particular drives are notorious for exceedingly high failure rates. Two failures out of seven on consecutive days isn't even particularly unlikely at this age for these drives!

Going forward, what you should do is:

Maintain backups. Remember that RAID is imperfect; critical data should always have offsite backups.
Try to purchase drives that aren't all from the same batch. That reduces the likelihood of consecutive failures.
Avoid very large arrays. Better to split into multiple logical volumes if possible, and maybe use smaller physical drives. Otherwise, mirrored RAID is better (faster rebuild) at the cost of more unusable physical space.

Bob

Posted 2015-08-26T01:23:02.223

Reputation: 51 526

Thank you for your reply. 1) RAID10 should be used instead of RAID6? Is it worth the more space it require for mirroring? 2) The capacity is required, and in the future those disk will be replaced with 6TB HDD (as originally posted). Would it be essencial to use RAID10 or RAID6 will be enough with a daily backup system? A new 6TB disk will be bought everytime an old 3TB fails. This prevent to have all disks from the same batch? – Perocat – 2015-08-26T02:56:17.977

@Perocat You should have backups regardless of which RAID format you use. RAID10 would certainly be faster than RAID6 (especially on rebuild), but the tradeoff is less available space - it's up to you which one you use. If you can stagger the purchases, that would help. – Bob – 2015-08-26T04:21:59.743

With 6TB WD Red is RAID6 reliable in terms of URE, etc.? Cause I read some articles about the dead of RAID5 in 2009 (with disk above 2TB). I always do backups! – Perocat – 2015-08-26T04:50:39.717

@Perocat Reliability isn't absolute. You need to keep in mind that you're going to have a ridiculously long rebuild time with 6TB drives - and you're at higher risk during that time. With two redundant disks, that might be an acceptable risk. As far as UREs... you're probably going to want to semi-frequently scrub the array just to make sure. Those drives are still relatively new so there isn't that much hard data on long-term reliability. – Bob – 2015-09-07T07:48:06.053

I suspect this will be closed as too broad. Too many questions. – Xavierjazz – 2015-08-26T01:29:29.620

Maybe... but all the questions are connected to a unique subject – Perocat – 2015-08-26T01:30:24.720

Well they are identical disk, why should they not fail the same given the same conditions. I would swap to disks rated to RAID use ASAP. Sounds like you need to do a lot of testing of your kit to me. – albal – 2015-08-26T01:38:32.493

WD Red HHD for NAS? – Perocat – 2015-08-26T02:23:43.723

RAID Disk failure - one per day (3ware 9650SE - Seagate Barracuda 3TB)

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