Re: Replacing the external log device

[Christoph Hellwig <hch@infradead.org>]

On Wed, Apr 12, 2023 at 09:21:32AM +0200, Ansgar Esztermann-Kirchner wrote:
> However, I've been bitten by a nasty problem twice in recent weeks: in
> the first instance, I wanted to replace a bunch of disks in a machine
> (something like 4x10TB to 4x16TB). Usually, we do that by setting up a
> new machine, rsyncing all the data, and then swap the machines. In
> this instance, I refrained from swapping the machines (due to lack of
> hardware), and merely swapped the disks. Initially, the kernel refused
> to mount the new disks (this was expected: the UUID of the log was
> incorrect, as I only swapped the HDDs, not the log device).

Let me restate that:  you created a new XFS file system, but then tried
to reuse an existing log device for it?

How did you format the new file system?  XFS either expects and internal
log, or a log device?  For the above error it must have been formatted
with a different external log?  And then you just switched the mount
option to the log device of the previous file system?

If so that can't work, and I'm surprised you got so far.