Drive failed in 3 disk RAID5 array

Over Clocker

Over Clocker

Over Clocker

Man of Honour
Joined
17 Oct 2002
Posts
9,712
Location
Retired Don
Hi guys,

If 1 drive fails in a RAID 5 array with 3 disks, and the system is no longer bootable, what will the process be once that disk is replaced? Will data be lost of will the array rebuild?

Cheers guys,

Mal :)
 
Raid 5 is very resilient, and your data should be intact once you replace the failed disk, and allow the raid to reconstruct itself. Many "hardware" raid5 solutions will continue full operation with a disk missing, but it takes quite a bit of computing power to do this.

Im guessing your raid5 array is software based, and it doesnt want to use all the CPU power recalculating the array on the fly.
 
Over Clocker said:
If 1 drive fails in a RAID 5 array with 3 disks, and the system is no longer bootable, what will the process be once that disk is replaced? Will data be lost of will the array rebuild?
Click to expand...
The system should still be bootable if the array goes critical - all the data is can still be regenerated (although with a performance hit). All that happens is you add in the new disk and the array goes away and rebuilds in the background.

crazyDAJT said:
but another disc could always fails during rebuild, then you will be screwed.
Click to expand...
Nope, nothing happens to the data on the other disks so all that happens is the array goes critical again and if you stick another new disk in the rebuild will start again.
 
rpstewart said:
Nope, nothing happens to the data on the other disks so all that happens is the array goes critical again and if you stick another new disk in the rebuild will start again.
Click to expand...

I was under the impression if one of the old discs in the array die (as this is more likely than the new one) then its all over.
 
Last edited:
It is if you lose 2 disks in a 3 disk raid 5 array (before the first one to die has been replaced and it's rebuilt itself), but once it's rebuilt itself using the replacement disk it's back to normal and it can take one disk out of 3 failing again (you just have to hope you never lose 2 disks at the same time).
 
Werewolf said:
It is if you lose 2 disks in a 3 disk raid 5 array (before the first one to die has been replaced and it's rebuilt itself), but once it's rebuilt itself using the replacement disk it's back to normal and it can take one disk out of 3 failing again (you just have to hope you never lose 2 disks at the same time).
Click to expand...

And thats the reason your 3 disks should all be sourced from different manufacturers/different batches if the same manufacturer... Well, for a high degree of fault tolerence thats what we do. The chance of simultaneous failure is vastly reduced.

Sam C
 
crazyDAJT said:
I was under the impression if one of the old discs in the array die (as this is more likely than the new one) then its all over.
Click to expand...
Misread the original post, I thought you meant the new drive dying. If one of the original disks dies then yes, you are boned.
 
You must log in or register to reply here.
Back
Top Bottom