[CentOS] Re: Raid5 issues

[Toby Bluhm]

Russ wrote:
> I ran the manufacturers tests, and it failed again on the short test with the media error and the long test fixed it.  I will be exchanging the drive for a new one, but for now its up and running.  
>
> This incident, however, has reinforced what I've read in many places - raid 5 is not safe.  If during a rebuild a media error is encountered, you lose all your data.  
>
> I would like to set up raid 10 instead, but it doesn't seem like its supported by my mdadm - the proper personalities are not loaded.  How do I get the raid10 personality in there?  
>
> Assuming I get the raid10 personality in there, how do I concert to raid10?  I suppose I can fail one of the drives in the raid5, set up a filesystem on it, copy the data from the raid5, kill the raid5, set up a raid10 from the three disks in the raid5 set with one missing, copy the data from the single drive, and add the single drive to the raid10 array.  Is this the right path?  Would I just cp certain directories over or use something like dd?  
>
> Any help would be greatly appreciated.  
>
> Russ
> Sent wirelessly via BlackBerry from T-Mobile.  
>
>   

. . . snipped top post . . .


I don't believe there's a raid10 personality. What you would do is build 
your 2 stripe sets, then mirror those striped md's. I tried that sort of 
thing a few years ago and it seemed to work, but I don't remember 
exactly how well it worked - may have been flakey at boot time - I did 
not spend much time on it.

Could also try raid5 with a hot spare or raid6.

I've been there with not trusting the HDs. I once had a bunch of new 
Maxtors scsi disks in a raid set and several failed in succession - they 
got swapped out with Seagates right quick.

-- 
Toby Bluhm
Midwest Instruments Inc.
30825 Aurora Road Suite 100
Solon Ohio 44139
440-424-2250