From mboxrd@z Thu Jan 1 00:00:00 1970
Return-Path: <pve-devel-bounces@lists.proxmox.com>
Received: from firstgate.proxmox.com (firstgate.proxmox.com [212.224.123.68])
by lore.proxmox.com (Postfix) with ESMTPS id 1E0B41FF15E
for <inbox@lore.proxmox.com>; Tue, 17 Jun 2025 12:01:48 +0200 (CEST)
Received: from firstgate.proxmox.com (localhost [127.0.0.1])
by firstgate.proxmox.com (Proxmox) with ESMTP id 3BD111B3B4;
Tue, 17 Jun 2025 12:02:15 +0200 (CEST)
Message-ID: <a4d7b7ff-741e-4490-bc0b-e16408b6b29e@proxmox.com>
Date: Tue, 17 Jun 2025 12:02:11 +0200
MIME-Version: 1.0
User-Agent: Mozilla Thunderbird
To: Proxmox VE development discussion <pve-devel@lists.proxmox.com>
References: <20250612140253.106555-1-f.ebner@proxmox.com>
<20250612140253.106555-21-f.ebner@proxmox.com>
<mailman.393.1750072060.395.pve-devel@lists.proxmox.com>
Content-Language: en-US
From: Fiona Ebner <f.ebner@proxmox.com>
In-Reply-To: <mailman.393.1750072060.395.pve-devel@lists.proxmox.com>
X-SPAM-LEVEL: Spam detection results: 0
AWL -0.031 Adjusted score from AWL reputation of From: address
BAYES_00 -1.9 Bayes spam probability is 0 to 1%
DMARC_MISSING 0.1 Missing DMARC policy
KAM_DMARC_STATUS 0.01 Test Rule for DKIM or SPF Failure with Strict Alignment
SPF_HELO_NONE 0.001 SPF: HELO does not publish an SPF Record
SPF_PASS -0.001 SPF: sender matches SPF record
Subject: Re: [pve-devel] [PATCH qemu-server 20/22] blockdev: add helpers to
generate blockdev commandline
X-BeenThere: pve-devel@lists.proxmox.com
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: Proxmox VE development discussion <pve-devel.lists.proxmox.com>
List-Unsubscribe: <https://lists.proxmox.com/cgi-bin/mailman/options/pve-devel>,
<mailto:pve-devel-request@lists.proxmox.com?subject=unsubscribe>
List-Archive: <http://lists.proxmox.com/pipermail/pve-devel/>
List-Post: <mailto:pve-devel@lists.proxmox.com>
List-Help: <mailto:pve-devel-request@lists.proxmox.com?subject=help>
List-Subscribe: <https://lists.proxmox.com/cgi-bin/mailman/listinfo/pve-devel>,
<mailto:pve-devel-request@lists.proxmox.com?subject=subscribe>
Reply-To: Proxmox VE development discussion <pve-devel@lists.proxmox.com>
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: 7bit
Errors-To: pve-devel-bounces@lists.proxmox.com
Sender: "pve-devel" <pve-devel-bounces@lists.proxmox.com>
Am 16.06.25 um 13:07 schrieb DERUMIER, Alexandre via pve-devel:
>>> The 'snapshot' option, for QEMU's snapshot mode, i.e. writes are only
>>> temporary, is not yet supported.
>
> from qemu manpage:
>
> "
> -snapshot
> Write to temporary files instead of disk image files. In
> this case, the raw disk image you use is not written back. You can
> however force the write back by pressing C-a s (see the Disk Images
> chapter in the System Emulation Users Guide).
>
> WARNING:
> snapshot is incompatible with -blockdev (instead use
> qemu-img to manually create snapshot images to attach to your
> blockdev). If you have mixed -blockdev and -drive declarations you can
> use the 'snapshot' property on your drive declarations instead of this
> global
> option.
> "
>
> So, if we want to keep this option. (I never used it to be honest),
I've briefly talked with Fabian about this a while ago. Yes, we do want
to keep it and it will be useful for
https://bugzilla.proxmox.com/show_bug.cgi?id=5187#c3
> I think we should create a temporary qcow2 file at vm start and delete
> it at vm stop.
Yes, we need an overlay. Note that there already is a FIXME comment too ;)
>> + # FIXME use overlay and new config option to define storage for temp write device
>> + die "'snapshot' option is not yet supported for '-blockdev'\n" if $drive->{snapshot};
> I'm not sure of current behaviour when you use a block device ?
Note that what you linked above is for the global '-snapshot' option,
not the drive one. It just doesn't apply to blockdevs AFAIU.
> how qemu known where to write a temp snapshot file ?
It just uses /var/tmp which of course is not ideal.
> maybe we could reuse state storage ? only with a temp qcow2 file ? or
> do we want to reuse snapshot feature of storage ?
We want to add a dedicated option to select a snapshot storage. There
could be a sensible default selection (depending on restrictions for the
overlay image).
> Also, I think that some features should be disable when it's used.
> (vm snapshots for example, maybe move disk,...)
Haven't looked into that, but would be pre-existing issues, so nothing
urgent. We just shouldn't break the feature if not necessary. If we
really don't get around to support it in time for PVE 9 we could also
initially note it as a breaking change or fallback to -drive.
_______________________________________________
pve-devel mailing list
pve-devel@lists.proxmox.com
https://lists.proxmox.com/cgi-bin/mailman/listinfo/pve-devel