On Tue, Nov 15, 2011 at 09:33:14AM -0500, Phillip Susi wrote:
> On 11/15/2011 4:22 AM, Ilya Dryomov wrote:
> >Restriper won't let you do raid1 -> dup transition because dup is only
> >allowed for a single-spindle FS, so you'll end up with error "btrfs:
> >unable to start restripe ...".
> >
> >There is no way to prioritize disks during restripe. To get dup back
> >you'll have to convert everything to single, remove the second drive and
> >then convert metadata from single to dup.
>
> So there is no way to put a disk into read only mode and prevent
> allocations of new chunks there?
>
> It seems like both of these limitations are highly undesirable when
> trying to recover from a failing disk. You don't want any more data
> being written to the failing disk while you are trying to remove it,
> and you certainly don't want to drop back to a single copy of data
> that is then written to the failing disk.
If you have a failing disk in a raid setup, you don't need to downgrade
your raid, you can add a third drive and remove the failing one. But
that's inconvenient and most of the time you'll have to do a full
balance.
So another thing I'm working on is drive swap, when it's done it will
take care of the failing disk scenario. If you have a raid setup and
one of the disks gone bad you'll be able to say
btrfs device replace FAILED NEW <mountpoint>
and it will put valid copy onto the fresh drive, basically doing a raid
rebuild.
Thanks,
Ilya
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