From mboxrd@z Thu Jan 1 00:00:00 1970 MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Date: Mon, 03 Jun 2019 21:23:39 +0200 From: Gionatan Danti In-Reply-To: <20190603132327.GA32187@reti> References: <93f53408-2f37-dec3-5c68-deef021f530c@assyoma.it> <20190603132327.GA32187@reti> Message-ID: <512bbf893225a1b4f6897b7540b09d1c@assyoma.it> Subject: Re: [linux-lvm] =?utf-8?q?Fast_thin_volume_preallocation=3F?= 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: Joe Thornber Il 03-06-2019 15:23 Joe Thornber ha scritto: > On Fri, May 31, 2019 at 03:13:41PM +0200, Gionatan Danti wrote: > >> - does standard lvmthin support something similar? If not, how do you >> see a >> zero coalesce/compression/trim/whatever feature? > > There isn't such a feature as yet. Ok, so the NAS vendor did something custom/proprietary. This is a reason why I do *not* like such devices: how much testing and verification are done before and after such customization? Not a lot, I would say. > With the next iteration of thin I'd like to > get away from the fixed allocation block sizes that we're using which > should greatly > reduce the number of mappings that we need to create to provision a > thick volume and > so speed it up a lot. Interesting. Do you plan to have an dynamic chunk size bound to some minumum/maximum? If so, how do you plan to tackle situations where a single big chunk should be split due to a small CoW write happening inside the big chunk? Example: a 128MB chunk-sized thin LV which is snapshotted and a small 4K writes happening at offset 32M from chunk start. > Presumably you want a thick volume but inside a thin pool so that you > can used snapshots? > If so have you considered the 'external snapshot' feature? Yes, in some cases they are quite useful. Still, a fast volume allocation can be an handy addition. -- Danti Gionatan Supporto Tecnico Assyoma S.r.l. - www.assyoma.it email: g.danti@assyoma.it - info@assyoma.it GPG public key ID: FF5F32A8