Subject: Re: RAID advice please ?
To: None <>
From: Greg Oster <>
List: current-users
Date: 04/06/2000 16:30:15
Jason R Thorpe writes:
> On Thu, Apr 06, 2000 at 06:17:11PM +0200, Manuel Bouyer wrote:
>  > For now I added a 'raidctl -P raid0' call in /etc/rc just before fsck,
>  > but the problem is that after an unclean shutdown it will take a very
>  > long time to reboot, because it'll have to revrite the parity before
>  > starting fsck. As I'll have about 10 raid1 sets on the machine this
>  > is not very good.
> Well, RAID-1 (mirroring only) shouldn't need a parity rewrite anyhow.  What
> am I missing here?

The "parity" on the RAID-1 set is the "mirror".  And, of course, the mirror 
(parity) needs to be in sync with the 'master'...  so yes, you *do* need 
to do the 'raidctl -P' on a RAID 1 set, if it says the parity is not 'clean'.

>  > What are the problems of starting a parity revrite in backround ?

Shouldn't be any, other than if you try to do them all at once you'll be 
thrashing all over the disks (assuming you have multiple components (for 
different RAID sets) per disk).. (I've got some ideas on how to solve this
(e.g. with a simple script that does the parity re-writes in a user-specified 
order), but havn't had a chance to test anything :( )

>  > This should allow the machine to continue to boot while parity is being
>  > rewriten.
> I thought Greg had implemented that (including progress meter! :-)

This part hasn't been completely worked out yet :(  (But yes, there is a 
progress meter :) )


Greg Oster