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From: Fabio Fantoni via pve-devel <pve-devel@lists.proxmox.com>
To: "DERUMIER, Alexandre" <alexandre.derumier@groupe-cyllene.com>,
	"pve-devel@lists.proxmox.com" <pve-devel@lists.proxmox.com>,
	"f.gruenbichler@proxmox.com" <f.gruenbichler@proxmox.com>
Cc: Fabio Fantoni <fabio.fantoni@m2r.biz>
Subject: Re: [pve-devel] [PATCH v3 qemu-server 11/11] qcow2: add external snapshot support
Date: Mon, 20 Jan 2025 15:29:39 +0100	[thread overview]
Message-ID: <mailman.24.1737383389.336.pve-devel@lists.proxmox.com> (raw)
In-Reply-To: <3307ec388a763510ec78f97ed9f0de00c87d54b5.camel@groupe-cyllene.com>

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From: Fabio Fantoni <fabio.fantoni@m2r.biz>
To: "DERUMIER, Alexandre" <alexandre.derumier@groupe-cyllene.com>, "pve-devel@lists.proxmox.com" <pve-devel@lists.proxmox.com>, "f.gruenbichler@proxmox.com" <f.gruenbichler@proxmox.com>
Subject: Re: [pve-devel] [PATCH v3 qemu-server 11/11] qcow2: add external snapshot support
Date: Mon, 20 Jan 2025 15:29:39 +0100
Message-ID: <6bdfe757-ae04-42e1-b197-c9ddb873e353@m2r.biz>

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
>> <support by default
> 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)


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  parent reply	other threads:[~2025-01-20 14:29 UTC|newest]

Thread overview: 68+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <20241216091229.3142660-1-alexandre.derumier@groupe-cyllene.com>
2024-12-16  9:12 ` [pve-devel] [PATCH v1 pve-qemu 1/1] add block-commit-replaces option patch Alexandre Derumier via pve-devel
2025-01-08 13:27   ` Fabian Grünbichler
2025-01-10  7:55     ` DERUMIER, Alexandre via pve-devel
     [not found]     ` <34a164520eba035d1db5f70761b0f4aa59fecfa5.camel@groupe-cyllene.com>
2025-01-10  9:15       ` Fiona Ebner
2025-01-10  9:32         ` DERUMIER, Alexandre via pve-devel
     [not found]         ` <1e45e756801843dd46eb6ce2958d30885ad73bc2.camel@groupe-cyllene.com>
2025-01-13 14:28           ` Fiona Ebner
2025-01-14 10:10             ` DERUMIER, Alexandre via pve-devel
2024-12-16  9:12 ` [pve-devel] [PATCH v3 qemu-server 01/11] blockdev: cmdline: convert drive to blockdev syntax Alexandre Derumier via pve-devel
2025-01-08 14:17   ` Fabian Grünbichler
2025-01-10 13:50     ` DERUMIER, Alexandre via pve-devel
2024-12-16  9:12 ` [pve-devel] [PATCH v3 pve-storage 1/3] qcow2: add external snapshot support Alexandre Derumier via pve-devel
2025-01-09 12:36   ` Fabian Grünbichler
2025-01-10  9:10     ` DERUMIER, Alexandre via pve-devel
     [not found]     ` <f25028d41a9588e82889b3ef869a14f33cbd216e.camel@groupe-cyllene.com>
2025-01-10 11:02       ` Fabian Grünbichler
2025-01-10 11:51         ` DERUMIER, Alexandre via pve-devel
     [not found]         ` <1caecaa23e5d57030a9e31f2f0e67648f1930d6a.camel@groupe-cyllene.com>
2025-01-10 12:20           ` Fabian Grünbichler
2025-01-10 13:14             ` DERUMIER, Alexandre via pve-devel
2024-12-16  9:12 ` [pve-devel] [PATCH v3 qemu-server 02/11] blockdev: fix cfg2cmd tests Alexandre Derumier via pve-devel
2024-12-16  9:12 ` [pve-devel] [PATCH v3 pve-storage 2/3] lvmplugin: add qcow2 snapshot Alexandre Derumier via pve-devel
2025-01-09 13:55   ` Fabian Grünbichler
2025-01-10 10:16     ` DERUMIER, Alexandre via pve-devel
2024-12-16  9:12 ` [pve-devel] [PATCH v3 qemu-server 03/11] blockdev : convert qemu_driveadd && qemu_drivedel Alexandre Derumier via pve-devel
2025-01-08 14:26   ` Fabian Grünbichler
2025-01-10 14:08     ` DERUMIER, Alexandre via pve-devel
2024-12-16  9:12 ` [pve-devel] [PATCH v3 pve-storage 3/3] storage: vdisk_free: remove external snapshots Alexandre Derumier via pve-devel
2024-12-16  9:12 ` [pve-devel] [PATCH v3 qemu-server 04/11] blockdev: vm_devices_list : fix block-query Alexandre Derumier via pve-devel
2025-01-08 14:31   ` Fabian Grünbichler
2025-01-13  7:56     ` DERUMIER, Alexandre via pve-devel
2024-12-16  9:12 ` [pve-devel] [PATCH v3 qemu-server 05/11] blockdev: convert cdrom media eject/insert Alexandre Derumier via pve-devel
2025-01-08 14:34   ` Fabian Grünbichler
2024-12-16  9:12 ` [pve-devel] [PATCH v3 qemu-server 06/11] blockdev: block_resize: convert to blockdev Alexandre Derumier via pve-devel
2024-12-16  9:12 ` [pve-devel] [PATCH v3 qemu-server 07/11] blockdev: nbd_export: block-export-add : use drive-$id for nodename Alexandre Derumier via pve-devel
2024-12-16  9:12 ` [pve-devel] [PATCH v3 qemu-server 08/11] blockdev: convert drive_mirror to blockdev_mirror Alexandre Derumier via pve-devel
2025-01-08 15:19   ` Fabian Grünbichler
2025-01-13  8:27     ` DERUMIER, Alexandre via pve-devel
     [not found]     ` <0d0d4c4d73110cf0e692cae0ee65bf7f9a6ce93a.camel@groupe-cyllene.com>
2025-01-13  9:52       ` Fabian Grünbichler
2025-01-13  9:55         ` Fabian Grünbichler
2025-01-13 10:47         ` DERUMIER, Alexandre via pve-devel
2025-01-13 13:42           ` Fiona Ebner
2025-01-14 10:03             ` DERUMIER, Alexandre via pve-devel
     [not found]             ` <fa38efbd95b57ba57a5628d6acfcda9d5875fa82.camel@groupe-cyllene.com>
2025-01-15  9:39               ` Fiona Ebner
2025-01-15  9:51                 ` Fabian Grünbichler
2025-01-15 10:06                   ` Fiona Ebner
2025-01-15 10:15                     ` Fabian Grünbichler
2025-01-15 10:46                       ` Fiona Ebner
2025-01-15 10:50                         ` Fabian Grünbichler
2025-01-15 11:01                           ` Fiona Ebner
2025-01-15 13:01                       ` DERUMIER, Alexandre via pve-devel
2025-01-16 14:56                     ` DERUMIER, Alexandre via pve-devel
2025-01-15 10:15                   ` DERUMIER, Alexandre via pve-devel
     [not found]         ` <c1559499319052d6cf10900efd5376c12389a60f.camel@groupe-cyllene.com>
2025-01-13 13:31           ` Fabian Grünbichler
2025-01-20 13:37             ` DERUMIER, Alexandre via pve-devel
2024-12-16  9:12 ` [pve-devel] [PATCH v3 qemu-server 09/11] blockdev: mirror: change aio on target if io_uring is not default Alexandre Derumier via pve-devel
2025-01-09  9:51   ` Fabian Grünbichler
2025-01-13  8:38     ` DERUMIER, Alexandre via pve-devel
2024-12-16  9:12 ` [pve-devel] [PATCH v3 qemu-server 10/11] blockdev: add backing_chain support Alexandre Derumier via pve-devel
2025-01-09 11:57   ` Fabian Grünbichler
2025-01-13  8:53     ` DERUMIER, Alexandre via pve-devel
2024-12-16  9:12 ` [pve-devel] [PATCH v3 qemu-server 11/11] qcow2: add external snapshot support Alexandre Derumier via pve-devel
2025-01-09 11:57   ` Fabian Grünbichler
2025-01-09 13:19     ` Fabio Fantoni via pve-devel
2025-01-20 13:44       ` DERUMIER, Alexandre via pve-devel
     [not found]       ` <3307ec388a763510ec78f97ed9f0de00c87d54b5.camel@groupe-cyllene.com>
2025-01-20 14:29         ` Fabio Fantoni via pve-devel [this message]
     [not found]         ` <6bdfe757-ae04-42e1-b197-c9ddb873e353@m2r.biz>
2025-01-20 14:41           ` DERUMIER, Alexandre via pve-devel
2025-01-13 10:08     ` DERUMIER, Alexandre via pve-devel
     [not found]     ` <0ae72889042e006d9202e837aac7ecf2b413e1b4.camel@groupe-cyllene.com>
2025-01-13 13:27       ` Fabian Grünbichler
2025-01-13 18:07         ` DERUMIER, Alexandre via pve-devel
2025-01-13 18:58           ` DERUMIER, Alexandre via pve-devel

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