Re: Mdadm won't rebuild a RAID5
On Monday 20 August 2007, martin f krafft wrote:
> also sprach Mike Bird <mgb-debian@yosemite.net> [2007.08.20.1627
+0200]:
> > > 3) RAID 5 is not resilient against multiple failures. We now use
> > > RAID 1. RAID 1 is also faster, although it sometimes requires
> > > more drives. In extreme cases we use RAID 1 with three or more
> > > drives.
> >
> > On Monday 20 August 2007 00:36, martin f krafft wrote:
> > > RAID 1 is also not resilient to multiple failures.
> >
> > Is the loss of N-1 members of an N-way RAID-1 not survivable?
>
> Well, yes. I see what you mean now. You can survive N-1 harddrives
> failing at once while with RAID5, that better not happen before
> a spare could take over.
In this case, I had 4 drives, so if one failed, then the spare should
have been added but that hadn't happened.
I've also tested the two "failed" drives and they are quite functional.
A friend made a point to me that could make a difference. I had not
partitioned the drives since mdadm seems okay without partitions. He
said even if I only use one drive-wide partition, I should still
partition the drives in a RAID first.
Fortunately, this was in a backup system so I can get new drives and
rebuild it from scratch with the larger drives. I've already got ideas
for using the "failed" drives that are proving to be just fine.
Hal
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