Removing a device from a metadata raid1 - data raid0

Removing a device from a metadata raid1 - data raid0

[Arnaud Kapp]

Hello,

I've setup a filesystem with 2 devices. The metadata are in raid1.
Data is in raid0.

I wish to remove one of this device from the filesystem (to use for an
unrelated purpose) but I am not able to do so.
It *seems* that attempting to balance metadata to dup is not allowed
(btrfs -mconvert=dup) because they currently are raid1.
The metadata in raid1 prevents me from removing the device because the
filesystem can't go below one device in raid1.

Could someone please advise me about my options here?

Thank you,

-- 
Kapp Arnaud - Xaqq

Re: Removing a device from a metadata raid1 - data raid0

[Hugo Mills]

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On Sat, May 23, 2015 at 12:15:13AM +0200, Arnaud Kapp wrote:
> Hello,
> 
> I've setup a filesystem with 2 devices. The metadata are in raid1.
> Data is in raid0.
> 
> I wish to remove one of this device from the filesystem (to use for an
> unrelated purpose) but I am not able to do so.
> It *seems* that attempting to balance metadata to dup is not allowed
> (btrfs -mconvert=dup) because they currently are raid1.
> The metadata in raid1 prevents me from removing the device because the
> filesystem can't go below one device in raid1.
> 
> Could someone please advise me about my options here?

   The RAID-0 data is also going to be a problem here. You'll have to
convert that to single, because RAID-0 requires a minimum of two
devices.

   For the metadata, one approach is to convert to single, delete the
device, then convert to DUP. That at least will work, if be a little
risky.

   IMO, we should definitely support conversion to DUP, and prevent
the automatic "upgrade" to RAID-1, but I think we don't at the moment.

   Hugo.

-- 
Hugo Mills             | Two things came out of Berkeley in the 1960s: LSD
hugo@... carfax.org.uk | and Unix. This is not a coincidence.
http://carfax.org.uk/  |
PGP: E2AB1DE4          |

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Re: Removing a device from a metadata raid1 - data raid0

[Arnaud Kapp]

Hello,

Yes the conversion from raid0 to single went fine.

>   For the metadata, one approach is to convert to single, delete the
> device, then convert to DUP. That at least will work, if be a little
> risky.

This worked great, thank you !


On Sat, May 23, 2015 at 12:22 AM, Hugo Mills <hugo@carfax.org.uk> wrote:
> On Sat, May 23, 2015 at 12:15:13AM +0200, Arnaud Kapp wrote:
>> Hello,
>>
>> I've setup a filesystem with 2 devices. The metadata are in raid1.
>> Data is in raid0.
>>
>> I wish to remove one of this device from the filesystem (to use for an
>> unrelated purpose) but I am not able to do so.
>> It *seems* that attempting to balance metadata to dup is not allowed
>> (btrfs -mconvert=dup) because they currently are raid1.
>> The metadata in raid1 prevents me from removing the device because the
>> filesystem can't go below one device in raid1.
>>
>> Could someone please advise me about my options here?
>
>    The RAID-0 data is also going to be a problem here. You'll have to
> convert that to single, because RAID-0 requires a minimum of two
> devices.
>
>    For the metadata, one approach is to convert to single, delete the
> device, then convert to DUP. That at least will work, if be a little
> risky.
>
>    IMO, we should definitely support conversion to DUP, and prevent
> the automatic "upgrade" to RAID-1, but I think we don't at the moment.
>
>    Hugo.
>
> --
> Hugo Mills             | Two things came out of Berkeley in the 1960s: LSD
> hugo@... carfax.org.uk | and Unix. This is not a coincidence.
> http://carfax.org.uk/  |
> PGP: E2AB1DE4          |



-- 
Kapp Arnaud - Xaqq