Re: multiple device usage

yanhai zhu
2008-12-28T13:26:11Z

> so i can do btrfs-vol -r /dev/sdb while it`s being mounted, pull the disk ,
> replace it with a bigger one, rescan-scsi-bus, mkfs.btrfs the new disk and
~~~~~~~~~~~~~~~~~~~~~~~
This step will fail, you will
get a "/dev/sdb is mounted" by mkfs.btrfs, but for other slots it's ok.

> then re-add - all while mount telling me, that /dev/sdb is still in use !?

2008/12/27 Roland <devzero@web.de>:
>>> i have some difficulty in understanding multi-device handling in depth.
>>>
>>> as
>>> http://btrfs.wiki.kernel.org/index.php/Using_Btrfs_with_Multiple_Devices
>>> tells,
>>>
>>> btrfs can span over multiple devices at the same time. (great feature,
>>> btw !)
>>>
>>> ok then:
>>>
>>> mkfs.btrfs -m single -d single /dev/sdb /dev/sdc - creates a btrfs
>>> spanning
>>> over /dev/sdb and sdc
>>>
>>> mount /dev/sdb /btrfs - mounts it
>>>
>>> btrfs-vol -b /btrfs - does a rebalancing of all data and metadata
>>>
>>> btrfs-vol -r /dev/sdc - removes one of the volumes and redistributes any
>>> extends in use on sdc to sdb (killer feature!!!)
>>>
>>> but what if i want to remove /dev/sdb ? (as that one is in use for the
>>> mount)
>>>
>>
>> Devices in btrfs are equal, so you can do this. The only glitch is
>> /proc/mounts and mount(8) get confused.
>
> so i can do btrfs-vol -r /dev/sdb while it`s being mounted, pull the disk ,
> replace it with a bigger one, rescan-scsi-bus, mkfs.btrfs the new disk and
> then re-add - all while mount telling me, that /dev/sdb is still in use !?
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--
Regards,
Zhu Yanhai