From: "Fabian Grünbichler" <f.gruenbichler@proxmox.com>
To: "DERUMIER, Alexandre" <alexandre.derumier@groupe-cyllene.com>,
"pve-devel@lists.proxmox.com" <pve-devel@lists.proxmox.com>
Subject: Re: [pve-devel] [PATCH v3 qemu-server 08/11] blockdev: convert drive_mirror to blockdev_mirror
Date: Mon, 13 Jan 2025 14:31:34 +0100 (CET) [thread overview]
Message-ID: <347515733.2990.1736775094981@webmail.proxmox.com> (raw)
In-Reply-To: <c1559499319052d6cf10900efd5376c12389a60f.camel@groupe-cyllene.com>
> DERUMIER, Alexandre <alexandre.derumier@groupe-cyllene.com> hat am 13.01.2025 11:47 CET geschrieben:
>
>
> >>something like this was what I was afraid of ;) this basically means
> >>we need to have some way to lookup the nodes based on the structure
> >>of the graph, which probably also means verifying that the structure
> >>matches the expected one (e.g., if we have X snapshots, we expect N
> >>nodes, if we currently have operation A going on, there should be an
> >>extra node, etc.pp. - and then we can "know" that the seventh node
> >>from the bottom must be snapshot 'foobar' ;)).
>
> I think it's not a much a problem to follow the graph from top to
> bottom. (as everything attached is have parent-child relationship)
> and
>
> - for snapshot, we have the snapshot name in the filename
> So we can known if it' a specific snap or the live image.
>
>
> for the temporary nodes (when we do block-add, before a mirror or
> switch), we define the nodename, so we don't need to parse the graph
> here.
>
>
>
> >>relying on $path being >>stable definitely won't work.
>
> I really don't see why the path couldn't be stable ?
>
> Over time, if something is changing in qemu (for example, rbd://....
> with a new param),
> it'll only be apply on the new qemu process (after restart or live
> migration), so the path in the block-node will be updated too. (live
> migration will not keep old block-nodes infos, the used value are qemu
> command line arguments)
>
>
> and the file path is the only attribute in a node that you can't
> update.
the path referenced in the running VM is stable. the path you are looking for in the graph is not. e.g., the path might be something some storage software returns. or udev. or .. and that can change with any software upgrade or not be 100% deterministic in the first place.
let's say you start the VM today and the path returned by the RBD storage plugin is /dev/rbd/XYZ, so that is how the blockdev is opened/the path is recorded. in two weeks, ceph gets updated and now the udev rule or the storage plugin code changes to return the more deterministic /dev/rbd/POOL/XYZ. now the paths don't match anymore. (this is just an example where such a thing happened in practice already ;)).
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next prev parent reply other threads:[~2025-01-13 13:31 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 [this message]
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
[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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