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From: "DERUMIER, Alexandre via pve-devel" <pve-devel@lists.proxmox.com>
To: "pve-devel@lists.proxmox.com" <pve-devel@lists.proxmox.com>,
	"f.gruenbichler@proxmox.com" <f.gruenbichler@proxmox.com>
Cc: "DERUMIER, Alexandre" <alexandre.derumier@groupe-cyllene.com>
Subject: Re: [pve-devel] [PATCH v4 pve-storage 1/5] qcow2: add external snapshot support
Date: Thu, 3 Apr 2025 04:27:59 +0000	[thread overview]
Message-ID: <mailman.539.1743654520.359.pve-devel@lists.proxmox.com> (raw)
In-Reply-To: <1188660913.4446.1743582515306@webmail.proxmox.com>

[-- Attachment #1: Type: message/rfc822, Size: 15495 bytes --]

From: "DERUMIER, Alexandre" <alexandre.derumier@groupe-cyllene.com>
To: "pve-devel@lists.proxmox.com" <pve-devel@lists.proxmox.com>, "f.gruenbichler@proxmox.com" <f.gruenbichler@proxmox.com>
Subject: Re: [pve-devel] [PATCH v4 pve-storage 1/5] qcow2: add external snapshot support
Date: Thu, 3 Apr 2025 04:27:59 +0000
Message-ID: <77db5694d7964d03a0673e3b8764a54a2e5c4147.camel@groupe-cyllene.com>

> >
> > > <this extends the storage API, so it should actually do that..
> > > and
> > > probably $backing should not be an arbitrary path, but something
> > > that
> > > is resolved locally?
> 
> I'll send the $snapname as param instead

>>see my comments on the qemu-server side, I think it would be even
>>better if we could just get rid of extending alloc_image like this,
>>and instead always go via volume_snapshot..

> 
> > > is this because it will automatically take the size from the
> > > backing
> > > image?
> 
> Yes, it take size from the backing.  (and refuse if you specify size
> param at the same time than backing file)

>>we pass a size and a backing file in qemu-server, so I guess that is
>>wrong there? ;)



About this part,  for the lvm plugin,  both size && backing is used.
size is used for allocate lvm device (but not in qcow2 format part,
where backing is ued).


Alloc_image is used by qemu-server to allocate the lvm volume, without
doing the volume rename part from volume_snapshot. (Because it must be
done in qemu-server to be able to rename online the volume).


so if you want to use volume_snapshot  from qemu-server, we need an
option to tell him to not rename because it's already done.
(previously, I was using it, and that why I was using  (if -e
volume_...), to continue if the volume was already renamed by qemu-
server.





> 


> This is more by security, I'm still unsure of the behaviour if you
> have
> multiple disks, and that snapshot is dying in the middle. (1 disk
> rename, the other not renamed). 

>>I am not sure what we gain by this other than papering over issues.
>>
>>for multi-disks what we'd need to do is:
>>- loop over volumes
>>-- take a snapshot of volume
>>-- as part of error handling directly in taking a snapshot, undo all
>>steps done until the point of error
>>- if an error occurs, loop over all already correctly snapshotted
>>volumes
>>-- undo snapshot of each such volume

ok, got it! I'll look to it for next patch version




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  reply	other threads:[~2025-04-03  4:28 UTC|newest]

Thread overview: 35+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <20250311102905.2680524-1-alexandre.derumier@groupe-cyllene.com>
2025-03-11 10:28 ` [pve-devel] [PATCH v4 pve-qemu 1/1] add block-commit-replaces option patch Alexandre Derumier via pve-devel
2025-03-11 10:28 ` [pve-devel] [PATCH v4 qemu-server 01/11] blockdev: cmdline: convert drive to blockdev syntax Alexandre Derumier via pve-devel
2025-03-11 10:28 ` [pve-devel] [PATCH v4 pve-storage 1/5] qcow2: add external snapshot support Alexandre Derumier via pve-devel
2025-04-01 13:50   ` Fabian Grünbichler
2025-04-02  8:01     ` DERUMIER, Alexandre via pve-devel
     [not found]     ` <0e2cd118f35aa8d4c410d362fea1a1b366df1570.camel@groupe-cyllene.com>
2025-04-02  8:28       ` Fabian Grünbichler
2025-04-03  4:27         ` DERUMIER, Alexandre via pve-devel [this message]
2025-03-11 10:28 ` [pve-devel] [PATCH v4 qemu-server 02/11] blockdev : convert qemu_driveadd && qemu_drivedel Alexandre Derumier via pve-devel
2025-03-11 10:28 ` [pve-devel] [PATCH v4 pve-storage 2/5] lvmplugin: add qcow2 snapshot Alexandre Derumier via pve-devel
2025-04-01 13:50   ` Fabian Grünbichler
2025-03-11 10:28 ` [pve-devel] [PATCH v4 qemu-server 03/11] replace qemu_block_set_io_throttle with qom-set throttlegroup limits Alexandre Derumier via pve-devel
2025-03-11 10:28 ` [pve-devel] [PATCH v4 pve-storage 3/5] storage: vdisk_free: remove external snapshots Alexandre Derumier via pve-devel
2025-04-01 13:50   ` Fabian Grünbichler
2025-04-07 11:02     ` DERUMIER, Alexandre via pve-devel
2025-04-07 11:29     ` DERUMIER, Alexandre via pve-devel
2025-03-11 10:28 ` [pve-devel] [PATCH v4 qemu-server 04/11] blockdev: vm_devices_list : fix block-query Alexandre Derumier via pve-devel
2025-04-02  8:10   ` Fabian Grünbichler
2025-04-11 17:32     ` DERUMIER, Alexandre via pve-devel
2025-03-11 10:28 ` [pve-devel] [PATCH v4 pve-storage 4/5] lvm: lvrename helper: allow path Alexandre Derumier via pve-devel
2025-04-01 13:50   ` Fabian Grünbichler
2025-03-11 10:28 ` [pve-devel] [PATCH v4 qemu-server 05/11] blockdev: convert cdrom media eject/insert Alexandre Derumier via pve-devel
2025-03-11 10:28 ` [pve-devel] [PATCH v4 pve-storage 5/5] lvm: add lvremove helper Alexandre Derumier via pve-devel
2025-04-01 13:50   ` Fabian Grünbichler
2025-03-11 10:29 ` [pve-devel] [PATCH v4 qemu-server 06/11] blockdev: block_resize: convert to blockdev Alexandre Derumier via pve-devel
2025-03-11 10:29 ` [pve-devel] [PATCH v4 qemu-server 07/11] blockdev: nbd_export: block-export-add : use drive-$id for nodename Alexandre Derumier via pve-devel
2025-03-11 10:29 ` [pve-devel] [PATCH v4 qemu-server 08/11] blockdev: convert drive_mirror to blockdev_mirror Alexandre Derumier via pve-devel
2025-03-11 10:29 ` [pve-devel] [PATCH v4 qemu-server 09/11] blockdev: change aio on target if io_uring is not default Alexandre Derumier via pve-devel
2025-03-11 10:29 ` [pve-devel] [PATCH v4 qemu-server 10/11] blockdev: add backing_chain support Alexandre Derumier via pve-devel
2025-04-02  8:10   ` Fabian Grünbichler
2025-03-11 10:29 ` [pve-devel] [PATCH v4 qemu-server 11/11] qcow2: add external snapshot support Alexandre Derumier via pve-devel
2025-04-02  8:10   ` Fabian Grünbichler
2025-04-03  4:51     ` DERUMIER, Alexandre via pve-devel
2025-04-04 11:31     ` DERUMIER, Alexandre via pve-devel
     [not found]     ` <3e516016a970e52e5a1014dbcd6cf9507581da74.camel@groupe-cyllene.com>
2025-04-04 11:37       ` Fabian Grünbichler
2025-04-04 13:02         ` DERUMIER, Alexandre via pve-devel

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