Re: [pve-devel] Unable to create persistent dirty-bitmap

Re: [pve-devel] Unable to create persistent dirty-bitmap

[DERUMIER, Alexandre via pve-devel]

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From: "DERUMIER, Alexandre" <alexandre.derumier@groupe-cyllene.com>
To: "pve-devel@lists.proxmox.com" <pve-devel@lists.proxmox.com>, "Prashant.Gamepatil@arctera.io" <Prashant.Gamepatil@arctera.io>
Subject: Re: Unable to create persistent dirty-bitmap
Date: Tue, 23 Sep 2025 09:30:21 +0000
Message-ID: <e88c612071187386f7178a4d519fad7c7f39ab09.camel@groupe-cyllene.com>

>>-------- Message initial --------
>>De: Prashant Patil <Prashant.Gamepatil@arctera.io>
>>À: Proxmox VE development discussion <pve-devel@lists.proxmox.com>
>>Objet: Unable to create persistent dirty-bitmap
>>Date: 23/09/2025 07:23:26

>>Hello,
>>We have configured 'Directory' storage having SAN as backing storage,
>>the SAN storage is mounted at file system path (/mnt/pve/SAN-
>>Storage1) with type ext4. We have couple of VMs running on this
>>storage. When we try to create a persistent bitmap on qcow2 file then
>>that fails with below error. The disk at 'scsi0' is "scsi0: SAN-
>>Storage1:101/vm-101-disk-1.qcow2,iothread=1,size=32G". So, the
>>question here is, why are we getting error to create persistent
>>bitmap for qcow2 disk?
>>
>>root@be1-proxmox1:~# echo '{"execute": "qmp_capabilities"}{"execute":
>>"block-dirty-bitmap-add", "arguments": {"node":"drive-
>>scsi0","name":"bm_1","persistent":true}}' | socat - unix-
>>connect:/var/run/qemu-server/101.qmp
>>{"QMP": {"version": {"qemu": {"micro": 2, "minor": 0, "major": 10},
>>"package": "pve-qemu-kvm_10.0.2-4"}, "capabilities": []}}
>>{"return": {}}
>>{"error": {"class": "GenericError", "desc": "Can't store persistent
>>bitmaps to drive-scsi0: Operation not supported"}}
>>root@be1-proxmox1:~#


I'm not 100% sure, but maybe is it the wrong node ? (on machine model
10, with blockdev enable, we use a throttle node at top node ("drive-
scsi0"),  
maybe it need to be done on the "format" node where qcow2 is available

for example:

 -blockdev '{"driver":"throttle","file":{"cache":{"direct":true,"no-
flush":false},"driver":"qcow2","file":{"aio":"io_uring","cache":{"direc
t":true,"no-flush":false},"detect-
zeroes":"unmap","discard":"unmap","driver":"file","filename":"/var/lib/
vz/images/8006/vm-8006-disk-0.qcow2","node-
name":"edd19f6c1b3a6d5a6248c3376a91a16","read-only":false},"node-
name":"fdd19f6c1b3a6d5a6248c3376a91a16","read-only":false},"node-
name":"drive-virtio0","throttle-group":"throttle-drive-virtio0"}'

you should use the node "fdd19f6c1b3a6d5a6248c3376a91a16"

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Re: [pve-devel] Unable to create persistent dirty-bitmap

[Prashant Patil via pve-devel]

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From: Prashant Patil <Prashant.Gamepatil@arctera.io>
To: "DERUMIER, Alexandre" <alexandre.derumier@groupe-cyllene.com>, "pve-devel@lists.proxmox.com" <pve-devel@lists.proxmox.com>
Subject: RE: Unable to create persistent dirty-bitmap
Date: Tue, 23 Sep 2025 10:16:48 +0000
Message-ID: <SA5PPFA482AF7CB2ED9FA29E8032762B5A6E31DA@SA5PPFA482AF7CB.namprd16.prod.outlook.com>

The qcow2 disk is at scsi0 slot, hence I think that is the correct node. Please let me know if otherwise.

Thanks
Prashant

-----Original Message-----
From: DERUMIER, Alexandre <alexandre.derumier@groupe-cyllene.com> 
Sent: 23 September 2025 03:00 PM
To: pve-devel@lists.proxmox.com; Prashant Patil <Prashant.Gamepatil@arctera.io>
Subject: Re: Unable to create persistent dirty-bitmap

>>-------- Message initial --------
>>De: Prashant Patil <Prashant.Gamepatil@arctera.io>
>>À: Proxmox VE development discussion <pve-devel@lists.proxmox.com>
>>Objet: Unable to create persistent dirty-bitmap
>>Date: 23/09/2025 07:23:26

>>Hello,
>>We have configured 'Directory' storage having SAN as backing storage, 
>>the SAN storage is mounted at file system path (/mnt/pve/SAN-
>>Storage1) with type ext4. We have couple of VMs running on this 
>>storage. When we try to create a persistent bitmap on qcow2 file then 
>>that fails with below error. The disk at 'scsi0' is "scsi0: SAN- 
>>Storage1:101/vm-101-disk-1.qcow2,iothread=1,size=32G". So, the 
>>question here is, why are we getting error to create persistent bitmap 
>>for qcow2 disk?
>>
>>root@be1-proxmox1:~# echo '{"execute": "qmp_capabilities"}{"execute":
>>"block-dirty-bitmap-add", "arguments": {"node":"drive- 
>>scsi0","name":"bm_1","persistent":true}}' | socat - unix- 
>>connect:/var/run/qemu-server/101.qmp
>>{"QMP": {"version": {"qemu": {"micro": 2, "minor": 0, "major": 10},
>>"package": "pve-qemu-kvm_10.0.2-4"}, "capabilities": []}}
>>{"return": {}}
>>{"error": {"class": "GenericError", "desc": "Can't store persistent 
>>bitmaps to drive-scsi0: Operation not supported"}} 
>>root@be1-proxmox1:~#


I'm not 100% sure, but maybe is it the wrong node ? (on machine model 10, with blockdev enable, we use a throttle node at top node ("drive- scsi0"), maybe it need to be done on the "format" node where qcow2 is available

for example:

 -blockdev '{"driver":"throttle","file":{"cache":{"direct":true,"no-
flush":false},"driver":"qcow2","file":{"aio":"io_uring","cache":{"direc
t":true,"no-flush":false},"detect-
zeroes":"unmap","discard":"unmap","driver":"file","filename":"/var/lib/
vz/images/8006/vm-8006-disk-0.qcow2","node-
name":"edd19f6c1b3a6d5a6248c3376a91a16","read-only":false},"node-
name":"fdd19f6c1b3a6d5a6248c3376a91a16","read-only":false},"node-
name":"drive-virtio0","throttle-group":"throttle-drive-virtio0"}'

you should use the node "fdd19f6c1b3a6d5a6248c3376a91a16"

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Re: [pve-devel] Unable to create persistent dirty-bitmap

[DERUMIER, Alexandre via pve-devel]

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From: "DERUMIER, Alexandre" <alexandre.derumier@groupe-cyllene.com>
To: "pve-devel@lists.proxmox.com" <pve-devel@lists.proxmox.com>, "Prashant.Gamepatil@arctera.io" <Prashant.Gamepatil@arctera.io>
Subject: Re: Unable to create persistent dirty-bitmap
Date: Tue, 23 Sep 2025 14:58:47 +0000
Message-ID: <2f69f3a87a1b7473df17f57dc658733a87059e0a.camel@groupe-cyllene.com>

>>The qcow2 disk is at scsi0 slot, hence I think that is the correct
>>node. Please let me know if otherwise.

I mean, It's not about slot, it's about blockdev graph (since pve9 +
machine version >= 10, we use the qemu blockdev, and it's a graph of
nodes)


Maybe this with machine version 9, it could work with drive-scsi0,

but since machine version 10, you need to find the "node" in the
blockdev graph

(you can use ps -aux to see the current qemu command line, to find the
node-name starting with "f" letter)

see me previous example:

 -blockdev '{"driver":"throttle","file":{"cache":{"direct":true,"no-
flush":false},"driver":"qcow2","file":{"aio":"io_uring","cache":{"direc

t":true,"no-flush":false},"detect-
zeroes":"unmap","discard":"unmap","driver":"file","filename":"/var/lib/

vz/images/8006/vm-8006-disk-0.qcow2","node-
name":"edd19f6c1b3a6d5a6248c3376a91a16","read-only":false},"node-
name":"fdd19f6c1b3a6d5a6248c3376a91a16","read-only":false},"node-
name":"drive-virtio0","throttle-group":"throttle-drive-virtio0"}'


the nodename is generate with:

https://git.proxmox.com/?p=qemu-server.git;a=blob;f=src/PVE/QemuServer/Blockdev.pm;h=8e6749e8be166dae0446fa162247ee1f4ce0272d;hb=HEAD

 114 my sub get_node_name {
 115     my ($type, $drive_id, $volid, $options) = @_;
 116 
 117     return fleecing_node_name($type, $drive_id) if $options-
>{fleecing};
 118     return tpm_backup_node_name($type, $drive_id) if $options-
>{'tpm-backup'};
 119 
 120     my $snap = $options->{'snapshot-name'};
 121 
 122     my $info = "drive=$drive_id,";
 123     $info .= "snap=$snap," if defined($snap);
 124     $info .= "volid=$volid";
 125 
 126     my $hash = substr(Digest::SHA::sha256_hex($info), 0, 30);
 127 
 128     my $prefix = "";
 129     if ($type eq 'alloc-track') {
 130         $prefix = 'a';
 131     } elsif ($type eq 'file') {
 132         $prefix = 'e';
 133     } elsif ($type eq 'fmt') {
 134         $prefix = 'f';
 135     } elsif ($type eq 'zeroinit') {
 136         $prefix = 'z';
 137     } else {
 138         die "unknown node type '$type'";
 139     }
 140     # node-name must start with an alphabetical character
 141     return "${prefix}${hash}";
 142 }

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[pve-devel] Unable to create persistent dirty-bitmap

[Prashant Patil via pve-devel]

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From: Prashant Patil <Prashant.Gamepatil@arctera.io>
To: Proxmox VE development discussion <pve-devel@lists.proxmox.com>
Subject: Unable to create persistent dirty-bitmap
Date: Tue, 23 Sep 2025 05:23:26 +0000
Message-ID: <SA5PPFA482AF7CB3F93BBC9D6DA1A512009E31DA@SA5PPFA482AF7CB.namprd16.prod.outlook.com>

Hello,
We have configured 'Directory' storage having SAN as backing storage, the SAN storage is mounted at file system path (/mnt/pve/SAN-Storage1) with type ext4. We have couple of VMs running on this storage. When we try to create a persistent bitmap on qcow2 file then that fails with below error. The disk at 'scsi0' is "scsi0: SAN-Storage1:101/vm-101-disk-1.qcow2,iothread=1,size=32G". So, the question here is, why are we getting error to create persistent bitmap for qcow2 disk?

root@be1-proxmox1:~# echo '{"execute": "qmp_capabilities"}{"execute": "block-dirty-bitmap-add", "arguments": {"node":"drive-scsi0","name":"bm_1","persistent":true}}' | socat - unix-connect:/var/run/qemu-server/101.qmp
{"QMP": {"version": {"qemu": {"micro": 2, "minor": 0, "major": 10}, "package": "pve-qemu-kvm_10.0.2-4"}, "capabilities": []}}
{"return": {}}
{"error": {"class": "GenericError", "desc": "Can't store persistent bitmaps to drive-scsi0: Operation not supported"}}
root@be1-proxmox1:~#

Thanks
Prashant

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