Re: evidence of persistent state, despite device disconnects

[Goffredo Baroncelli <kreijack@inwind.it>]

On 2016-01-09 11:55, Duncan wrote:
> (a minimum of two devices are required to create raid1 chunks, since two
> copies are required and they can't be on the same device).

I think that this is the problem: BTRFS should allocate a new chunk as RAID1, even if only one device is available. It is already capable to use a RAID1 chunk in degraded mode, so it shouldn't be so difficult to create new chunk RAID1 when only a one disk is available.

Anyway I agree with Chris about the fact that btrfs sometime gives incorrect information about the devices. In the past I proposed to abandon the current model where the device are "per-registered" before the mount command asynchronously.
I wrote a mount helper which does a scan at the mount time [1]; this would reduce the window time where a device disappearing could cause confusion.

BR
G.Baroncelli


[1] https://www.mail-archive.com/linux-btrfs@vger.kernel.org/msg39429.html
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