Re: Expanding RAID array?

[Brad Campbell <brad@wasp.net.au>]

Neil Brown wrote:

> - add disks to convert to raid6.
>     I don't think this is possible, but you should check the latest
>     raid reconfig.

It's not. I started work on it Feb last year but then real life got in the way again.
In the longer term, I think raidreconf as it stands is going to die (mainly because it's 
infrastructure relies on the old raidtab architecture). I thought about perhaps porting it as an 
addon to mdadm, but then I ran out of drives/machines/time to test it on.

>     Might be supported online with a limited raid6 in which the Q
>     syndrome (second 'parity' block) isn't rotated among disks.

In theory I would have thought it not that much different than a raid-5 expand, just inserting an 
extra block for the Q syndrome.

> - status of RAID6
>     I believe it is as stable/reliable as raid5.

Mine has been running since Feb last year with fairly moderate use and no hiccups.
I have just upgraded to the latest 2.6.15-git on that machine to give some of the newer raid patches 
(like check & repair) a whirl. Seems fairly solid.

Let's say I've never had any raid-6 related data loss, or even near misses, but it has saved my 
bacon in 2 dual drive failures in the last year.

Oh, and the new read and check code (rather than just rebuild the parity blocks) shaves about 1 hour 
of what was an 11 hour rebuild time on this particular raid-6. Thanks Neil!

Regards,
Brad
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