lost everything?

Max Waterman davidmaxwaterman at fastmail.co.uk
Wed May 4 14:07:57 UTC 2005

Dang, I'm sorry, I meant RAID5...doh...

I figured that losing 2 disks (or their common PCI card) in a RAID5 
would be fatal. Is that not so?

Well, it does seem that it wasn't fatal, since a '/sbin/mdadm --assemble 
--force /dev/md2 --scan' did the trick :D


Thorsten Jungblut wrote:
> Hi,
>>I had a 4 disk pata RAID0 with 1 sata spare.
>>The 4 disk pata array was made using 2 PCI card, 2 drives per card.
>>It seems that one of the cards was loose, and so I lost 2 drives at once.
>>Please tell me I haven't just lost everything on the array...
> If a card is lost, that doesn't mean the drives are defect now? You only 
> need to get a new card? If thats true, no data is lost at all, you just 
> can not access it until you get a new card.
> If one DRIVE fails, all data in a RAID0 is lost.
> A spare disk doesn't make sense for RAID0 since if a drive fails, the 
> array contents are lost and there is nothing that can be written to the 
> spare disk!
> Consider using a RAID5 over all disks without a spare. A RAID5 can handle 
> a single disk failure without data loss.
> A RAID5 consisting of n disks has n-1 the capacity of a single disk, the 
> same as a RAID0 with a "spare".
> Or use RAID0+1. A RAID0+1 consisting of n disks has the capacity of n/2 
> disks but it can handle a single disk failure and in some cases even more 
> disk failures depending on what disks fail.
> Viele Grüsse,
> Thorsten

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