Bug#688757: pvmove onto disk with different sector size hazardous

[Bastian Blank]

On Tue, Sep 25, 2012 at 02:45:47PM +0200, Daniel Pocock wrote:
> I have marked this `severe' because it has a high probability of
> filesystem corruption and drives with 4096 byte sectors are likely to
> become much more widespread.

This is a local problem. You have setup a filesystem with 512 bytes as
block size (xfs I presume) and expect it to work on larger blocks? Just
don't use xfs or kill the maintainer of xfs tools for still using such
tiny blocks.

> I recently purchased a 3TB drive and created one big 3TB partition for lvm

Which brand and model? All large disks I obtained in the last year shows
512 bytes sectors.

> Many errors appeared during the pvmove operation

And this would be?

> The old disk has 512 byte sectors and the new disk has 4096 byte sectors.

Please show smartctl -i $device.

> It appears that pvmove is potentially a lot more dangerous than the man
> page suggests.  Although they were mounted during the pvmove, they were
> not in use (they are backup filesystems and they only get written to on
> demand).  If they had open files at the time, I suspect that corruption
> would have occurred.

I doubt that, because the write would have been canceled.

> Some potential ideas:
> a) pvmove should check sector sizes and require --force if there is a
> mismatch

Nope. This is up to the admin. Also lvm does not know about the
filesystem.

Bastian

-- 
Vulcans do not approve of violence.
		-- Spock, "Journey to Babel", stardate 3842.4