From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <53201EF8.3020104@redhat.com> Date: Wed, 12 Mar 2014 09:46:48 +0100 From: Marian Csontos MIME-Version: 1.0 References: <0b4701cf3d86$4a25d8a0$de7189e0$@acm.org> In-Reply-To: <0b4701cf3d86$4a25d8a0$de7189e0$@acm.org> Content-Transfer-Encoding: 7bit Subject: Re: [linux-lvm] migrating a thick LV to a thin LV Reply-To: LVM general discussion and development List-Id: LVM general discussion and development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , List-Id: Content-Type: text/plain; charset="us-ascii"; format="flowed" To: LVM general discussion and development , henson@acm.org On 03/12/2014 01:01 AM, Paul B. Henson wrote: > I'm looking at converting a system to using thin provisioning, and have a > handful of existing fixed size LV's I want to migrate to the thinpool. > Ideally, after the migration they would also be thinly provisioned, only > taking up the amount of space they are actually using, not their existing > size. All of them have ext4 filesystems on them. > > One option would be to use resize2fs to shrink the filesystems down to their > bare minimum, resize the existing LV to that, dd it onto a thin LV of the > original size, and then run resize2fs again to bring the filesystem back to > full capacity without any blocks wasted. > > However, I was wondering if I just dd'd the existing LV onto a thin LV of > the same size, and then ran fstrim, would that release the unused space? I > see that thin pools support passing down discards to the underlying device, > but it's not clear whether they also process them internally, freeing up > space in the thinpool that is no longer in use by the thin LV. Yes, discarded blocks in the thin-pool data device which are not referenced from other thin-volumes (snapshots) are released regardless whether the device at the bottom supports discards or not. -- Martian > > Any thoughts? > > Thanks. > > > _______________________________________________ > linux-lvm mailing list > linux-lvm@redhat.com > https://www.redhat.com/mailman/listinfo/linux-lvm > read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/ >