Re: BTRFS messes up snapshot LV with origin

[Goffredo Baroncelli <kreijack@inwind.it>]

On 11/25/2014 11:21 PM, Zygo Blaxell wrote:
>> > However I still doesn't understood why you want btrfs-w/multiple disk over LVM ?
> I want to split a few disks into partitions, but I want to create,
> move, and resize the partitions from time to time.  Only LVM can do
> that without taking the machine down, reducing RAID integrity levels,
> hotplugging drives, or leaving installed drives idle most of the time.
> 
> I want btrfs-raid1 because of its ability to replace corrupted or lost
> data from one disk using the other.  If I run a single-volume btrfs
> on LVM-RAID1 (or dm-RAID1, or RAID1 at any other layer of the storage
> stack), I can detect lost data, but not replace it automatically from
> the other mirror.
OK, now I have understood.

Anyway as workaround, take in account that you can pass explicitly the
devices as:

mount -o device=/dev/sda,device=/dev/sdb,device=/dev/sdc /dev/sdd /mnt

(supposing that the filesystem is on /dev/sda.../dev/sdd)

I am working to a mount.btrfs helper. The aim of this helper is to manage
the assembling of multiple devices; the main points will be:
- wait until all the devices appeared
- allow (if required) to mount in degraded mode after a timeout
- at this point it could/should also skip the lvm-snapshotted devices (but before 
I have to know how recognize these) 

I hope to issue the patches in the next week

BR
G.Baroncelli

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