From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <51068238.1090809@redhat.com> Date: Mon, 28 Jan 2013 14:50:48 +0100 From: Marian Csontos MIME-Version: 1.0 References: <20130124155312.GA10563@daedalus.cslab.ece.ntua.gr> <20130124180834.GA3122@agk-dp.fab.redhat.com> <51017F0C.20100@bmsi.com> <20130124234235.GB3122@agk-dp.fab.redhat.com> <20130125084410.GB10563@daedalus.cslab.ece.ntua.gr> In-Reply-To: <20130125084410.GB10563@daedalus.cslab.ece.ntua.gr> Content-Transfer-Encoding: 7bit Subject: Re: [linux-lvm] Sparse LVs, --virtualsize equal to --size 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 Cc: synnefo-devel@googlegroups.com, Vangelis Koukis On 01/25/2013 09:44 AM, Vangelis Koukis wrote: > On Thu, Jan 24, 2013 at 11:42:35pm +0000, Alasdair G Kergon wrote: >> So look at thin provisioning with its zeroing option. >> External origin. (support currently being added to lvm) >> >> Or this not-yet-upstream target: >> http://people.redhat.com/agk/patches/linux/editing/dm-add-zeroed-target.patch >> >> Alasdair > > Thanks Alasdair, > > this seems to fit the bill perfectly, it's a shame it's > not yet merged upstream. > > Until then, if we are to go with the "snapshot-over-the-zero-target" > route, can you comment on quantifying the space overhead of tracking > chunks in the snapshot? Beware! Large old-style snapshots may take a very long time to activate[1] (reportedly up to few hours) and my guess is many smaller snapshots will behave the same[2], the total amount of chunks written to all snapshots being the key to slow start... You should definitely try it with your workflow before going too far that direction. [1]Just search for 'lvm large snapshot'. Someone here may be able to point you to a more complete data. [2] Not even trying to think about many larger ones as your usecase suggests: just update kernel and java few times and with journal FS you will soon be at few gigabytes per VM. -- Marian > > Thanks again, > Vangelis. > > > > > _______________________________________________ > 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/