From: Fiona Ebner <f.ebner@proxmox.com>
To: Proxmox VE development discussion <pve-devel@lists.proxmox.com>,
"f.gruenbichler@proxmox.com" <f.gruenbichler@proxmox.com>
Subject: Re: [pve-devel] [PATCH v3 qemu-server 08/11] blockdev: convert drive_mirror to blockdev_mirror
Date: Mon, 13 Jan 2025 14:42:29 +0100 [thread overview]
Message-ID: <78d1eb79-65fc-44a3-825f-5ca53ad04b8c@proxmox.com> (raw)
In-Reply-To: <mailman.245.1736765310.441.pve-devel@lists.proxmox.com>
Am 13.01.25 um 11:47 schrieb DERUMIER, Alexandre via pve-devel:
>>> 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.
I do think following the graph structure would be a viable approach too.
>>> relying on $path being >>stable definitely won't work.
>
> I really don't see why the path couldn't be stable ?
>
> Over time, if something is changing in qemu (for example, rbd://....
> with a new param),
> it'll only be apply on the new qemu process (after restart or live
> migration), so the path in the block-node will be updated too. (live
> migration will not keep old block-nodes infos, the used value are qemu
> command line arguments)
>
Upgrading libpve-storage-perl or an external storage plugin while the VM
is running could lead to a different result for path() and thus
breakage, right?
If we do need lookup, an idea to get around the character limit is using
a hash of the information to generate the node name, e.g.
hash("fmt-$volid@$snapname"), hash("file-$volid@$snapname") or whatever
is actually needed as unique information. Even if we only use lowercase
letters, we have 26 base chars, so 26^31 possible values.
So hashes with up to
>>> math.log2(26**31)
145.71363126237387
bits can still fit, which should be more than enough. Even with an
enormous number of 2^50 block nodes (realistically, the max values we
expect to encounter are more like 2^10), the collision probability
(using a simple approximation for the birthday problem) would only be
>>> d=2**145
>>> n=2**50
>>> 1 - math.exp(-(n*n)/(2*d))
1.4210854715202004e-14
>
> and the file path is the only attribute in a node that you can't
> update.
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next prev parent reply other threads:[~2025-01-13 13:43 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 [this message]
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
[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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