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From: Zdenek Kabelac <zkabelac@redhat.com>
To: LVM general discussion and development <linux-lvm@redhat.com>,
	Paul Dann <pdgiddie@gmail.com>
Subject: Re: [linux-lvm] lvreduce thin-pool
Date: Tue, 14 Jan 2020 13:21:49 +0100	[thread overview]
Message-ID: <dc48ee9f-d290-b7af-6a3d-1b105cee2c26@redhat.com> (raw)
In-Reply-To: <CALZj-VrVhXLSBTthE5nsL9wQVaTr2XgJRULRFKvNqi9CCbvV5A@mail.gmail.com>

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

      reply	other threads:[~2020-01-14 12:21 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-14  9:52 Paul Dann
2020-01-14 12:21 ` Zdenek Kabelac [this message]

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