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[79.18.78.119]) by smtp.googlemail.com with ESMTPSA id a640c23a62f3a-ab384ce0529sm617267166b.43.2025.01.20.06.29.40 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 20 Jan 2025 06:29:40 -0800 (PST) Message-ID: <6bdfe757-ae04-42e1-b197-c9ddb873e353@m2r.biz> Date: Mon, 20 Jan 2025 15:29:39 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [pve-devel] [PATCH v3 qemu-server 11/11] qcow2: add external snapshot support To: "DERUMIER, Alexandre" , "pve-devel@lists.proxmox.com" , "f.gruenbichler@proxmox.com" References: <20241216091229.3142660-1-alexandre.derumier@groupe-cyllene.com> <570013533.830.1736423850641@webmail.proxmox.com> <3307ec388a763510ec78f97ed9f0de00c87d54b5.camel@groupe-cyllene.com> Content-Language: it From: Fabio Fantoni In-Reply-To: <3307ec388a763510ec78f97ed9f0de00c87d54b5.camel@groupe-cyllene.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: quoted-printable X-Antivirus: Avast (VPS 250119-6, 19/1/2025), Outbound message X-Antivirus-Status: Clean X-SPAM-LEVEL: Spam detection results: 0 BAYES_00 -1.9 Bayes spam probability is 0 to 1% DKIM_SIGNED 0.1 Message has a DKIM or DK signature, not necessarily valid DKIM_VALID -0.1 Message has at least one valid DKIM or DK signature DMARC_PASS -0.1 DMARC pass policy JMQ_SPF_NEUTRAL 0.5 SPF set to ?all KAM_INFOUSMEBIZ 0.75 Prevalent use of .info|.us|.me|.me.uk|.biz|xyz|id|rocks|life domains in spam/malware RCVD_IN_DNSWL_NONE -0.0001 Sender listed at https://www.dnswl.org/, no trust SPF_HELO_NONE 0.001 SPF: HELO does not publish an SPF Record SPF_PASS -0.001 SPF: sender matches SPF record Il 20/01/2025 14:44, DERUMIER, Alexandre ha scritto: > Hi Fabio ! > >>> In this implementation I don't see the possibility of using them on >>> raw >>> disks (on files) from a fast look, or am I wrong? If so, why? I think >>> the main use would be in cases like that where you don't have >>> snapshot >> Ah, we have discussed about it with Fabian. the V1/v2 had raw support, > but I have removed it from v3 because it's simplify a lot the code, > and from my test, I don't see anymore too much difference between qcow2 > && raw. (maybe 10% diff max) > > Note that you can preallocated 100% the base qcow2 image if you want. > (or only metadatas, that's the defaut) > > > I'm going to do more extensive benchmark, but qcow2 have improved a lot > since last years (with sub-allocation clusters), so it should be too > far from a cow filesystem like zfs,btrfs. (sure, they are still > overhead vs a simple raw). > > > Thanks for your reply, I don't remember exactly when my tests date back (for external snapshot), it's been several years now, and I had done them on the default versions of Debian 10, I used, and still use on most servers, with libvirt.We had all the servers with enterprise hdd in raid1 or raid10 and the difference in performance between pre-allocated raw and qcow2, even just used with external snapshots was clearly visible (also without benchmark). I haven't had enough time for a few years to keep myself well informed about the virtualization part and do significant testing, I've recently started investing a lot of time in learning and testing again with proxmox, even though I didn't have many other things to manage. in recent years we use only or almost only ssd and nvme disks (on new or improved servers) and it is not necessary to have them pre-allocated, the latter are basically not pre-allocated and the proxmox ones (latest) with lvm-thin, however we are upgrading some servers (and we will do more) to proxmox keeping the existing storage on pre-allocated raw files and it would be useful for example to have snapshot support also in these cases, unfortunately since it is not based on libvirt I cannot do it even manually (in a fairly fast and safe way that I had tested and documented) from the command line and I do not know if it would be possible with some workarounds and more operations to force it even if not implemented in proxmox. I use qcow2 by default on my PCs (with libvirt though) for some test vms where I use snapshots quite a bit, but internal and from virt-manager, using on ssd/nvme and usually a single active vm I don't notice any particular performance problems, in truth I've never done any tests regarding performance on my workstations in this regard for this implementation instead I think it is important to measure and document in order to give enough information to users to make good choices (and seems you want do it) out of curiosity, besides the obvious cases where external snapshots would be useful, i.e. on raw files and on lvm (not lvm-thin), what other cases would be useful given that they already have snapshot support (qcow2 with the internal one, zfs, btrfs, lvm-thin etc)? not having it on raw files I think would take away a lot of its usefulness, but I could be wrong if there are uses I can't imagine, maybe make something more possible with replicas and migrations? (I haven't looked into it enough) -- Questa email =C3=A8 stata esaminata alla ricerca di virus dal software anti= virus Avast. www.avast.com --===============0087134748412145387== Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Disposition: inline _______________________________________________ pve-devel mailing list pve-devel@lists.proxmox.com https://lists.proxmox.com/cgi-bin/mailman/listinfo/pve-devel --===============0087134748412145387==--