Timeline for RAID-5: Two disks failed simultaneously?
Current License: CC BY-SA 3.0
19 events
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| Aug 11, 2014 at 12:19 | comment | added | kasperd | Not a very helpful answer. Sure, with a double disk failure on a RAID 5, chance of recovery is not good. But most double disk failures on RAID 5 are probably just a matter of one faulty disk and a few uncorrected read errors on other disks. If that's the case, recovering most of the data is still possible given the right tools. Pointers to such tools would be helpful. | |
| Aug 11, 2014 at 12:14 | audit | First posts | |||
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| Aug 7, 2014 at 23:17 | audit | First posts | |||
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| Jul 25, 2014 at 19:11 | comment | added | War | @thanby lol its not "right next to the tank" just close enough that a bit of pressure (caused by say a leak low down) might be able to reach it and i'm planning to move the tank just don't have the space atm to put it anywhere else as the replacement tank is in that space and its pretty large. | |
| Jul 25, 2014 at 11:52 | comment | added | thanby | @Wardy Just out of curiosity... whose idea was it to store your NAS next to a fish tank? Sounds like a more basic design flaw than which RAID you choose :p | |
| Jul 24, 2014 at 21:45 | comment | added | Basil | Raid levels all have their use. Raid 10 throws half your capacity out the window, but doesn't make anything calculate parity. A good controller will calculate parity well enough that it isn't that slow, and will have a cache that hides the write penalty even more. | |
| Jul 24, 2014 at 15:53 | comment | added | SnakeDoc | @Wardy RAID5 or RAID6 does not give the same performance as a RAID10, not even close. RAID5 and 6 get a read boost, but writes takes considerable longer. RAID10 has improved writes and reads. Depends on your expected i/o load. If you are running something write-intensive, such as a VM cluster, then you will benefit immensely from RAID10 in a 0 + 1 configuration. However, since the OP is considering a separate chassis, it's really a backup server with complete data set, so this point is moot. | |
| Jul 24, 2014 at 15:41 | comment | added | War | @basil reading back RAID 6 gives you the ability for 2 disks to fail, in my scenario with a pair of RAID 5 arrays I can have 3 disks fail across the 2 boxes or even all 5 in a single box and still be up and running :) and I don't have that expensive performance hit of RAID 6 with RAID 5 ... RAID 10 is a good option too I spose | |
| Jul 24, 2014 at 15:38 | comment | added | War | @SnakeDoc as stated above ... you are wrong Less Cost, same performance but no backup so if anything happens to that box you're screwed without replication. | |
| Jul 24, 2014 at 15:37 | comment | added | War | @Basil my solution here might be expensive but from it i effectively get 3 things 1. reliable data access, 2. high performance, 3. a backup of the first 2 with the same features that could be swapped in if need be with a simple dns update. There may be cheaper ways to do this but this is effectively how all the big players do it just with whole data centers. | |
| Jul 24, 2014 at 15:30 | comment | added | Basil | @Wardy I think I misread your comment- absolutely, having your data in another set of disks in another chassis is better than local raid. | |
| Jul 24, 2014 at 13:41 | comment | added | War | Yeh but if say ... the fish tank next to my nas springs a leak I lose everything because all disks would end up with salt water in them. And like what was suggested above, RAID is not a substitute for backups! | |
| Jul 23, 2014 at 20:33 | comment | added | SnakeDoc | @Wardy That is a lot of additional expense just to have a redundant (ie. mirrored) array. Just switch over to a RAID10, you will get much better write performance, plus you can loose half your disks and stay online (depending on which side of the mirrored raid 0's fail). Less cost, better performance. | |
| Jul 23, 2014 at 13:57 | comment | added | Basil | @Wardy, wouldn't raid 6 give you that? | |
| Jul 23, 2014 at 13:31 | comment | added | peterh | He has probably only a badblock on his disk3. I am really wondering why a professional sysadmin never heard from block-level copy tools. | |
| Jul 23, 2014 at 11:04 | comment | added | War | I use RAID5 on my 3TB 5 drive array, I was toying with getting a second array to use as a replicated copy of the first. That way for me to lose the data would require more than 1 disk to fail on both arrays at the same time (so I would need 4 disks) but still keeping that large amount fo the capacity available. Having read this I may now step up that time frame for getting the second array. | |
| Jul 22, 2014 at 16:18 | vote | accept | Mike Furlender | ||
| Nov 22, 2018 at 2:22 | |||||
| Jul 22, 2014 at 15:00 | comment | added | Sobrique | There's two problems with RAID5. One: rebuild time of 3TB, given a slow SATA drive can be large, making odds of a compound failure high. The other is the unrecoverable bit error rate - spec sheet on most SATA drives has 1 / 10 ^ 14, which is - approx - 12TB of data. With a 5 way, 3B RAID this becomes almost inevitable when a rebuild is needed. | |
| Jul 22, 2014 at 14:57 | history | answered | Basil | CC BY-SA 3.0 |