[linux-lvm] lvreduce thin-pool
Zdenek Kabelac
zkabelac at redhat.com
Tue Jan 14 12:21:49 UTC 2020
Dne 14. 01. 20 v 10:52 Paul Dann napsal(a):
> Hi there,
>
> I've been following Ede Wolf's thread with interest, but it hasn't quite
> covered my query, and I've not been able to find much about this in the archives:
>
> Are there any plans to implement reducing of thin pools? I've been bitten
> several times by carelessly allowing a thin pool to expand onto unsuitable
> storage and subsequently being unable to reduce the pool again to ensure IO
> performance of the pool. (I know that better forward planning can mitigate this.)
>
> Mainly, I'm wondering if there are technical reasons this hasn't been
> implemented yet? On the face of it, I'd have expected this to be a relatively
> straight-forward procedure? But I'd be interested in why this might not be the
> case.
Hi
There is no support for 'online' reduction of thin-pool. Mainly because there
is not much interest into this.
For 'offline' reduction - you could probably write a tool working like this:
In kernel metadata figure out who holds the last 'chunk' and find what is the
first 'empty' chunk - and copy the chunk there and remap all the references
to this last chunk to the new position.
Quite simple isn't :) - the task would be probably simpler to code if it
would be directly using thin tools from d-m-p-d package (i.e. thin_repair
background)
So basically a straight forward process, someone just needs to do all the
coding for this.
Regards
Zdenek
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