Can not backup template with SATA

[TReinhard]

Hi,

when I try to backup a vm-template with a SATA-Disk it fails:

...
INFO: include disk 'sata0' 'rbd:base-104-disk-0' 8G
INFO: creating Proxmox Backup Server archive 'vm/104/2021-04-26T07:19:00Z'
INFO: starting kvm to execute backup task
kvm: -device ide-hd,bus=ahci0.0,drive=drive-sata0,id=sata0,rotation_rate=1,bootindex=100: Block node is read-only
ERROR: Backup of VM 104 failed - start failed: QEMU exited with code 1
INFO: Failed at 2021-04-26 09:19:02
...

It works when I change the Disk type to SCSI:

...
INFO: include disk 'scsi0' 'rbd:base-104-disk-0' 8G
INFO: creating Proxmox Backup Server archive 'vm/104/2021-04-26T07:22:17Z'
INFO: starting kvm to execute backup task
INFO: started backup task '9dcd08b4-d347-4fd3-beaf-21d73a74f583'
INFO: 8% (684.0 MiB of 8.0 GiB) in 3s, read: 228.0 MiB/s, write: 0 B/s
...

It also works when I use SATA and remove the "tempalte" marking:

...
INFO: VM Name: opnsense
INFO: include disk 'sata0' 'rbd:base-104-disk-0' 8G
INFO: creating Proxmox Backup Server archive 'vm/104/2021-04-26T07:23:43Z'
INFO: starting kvm to execute backup task
INFO: started backup task '54813e9c-5db3-4e5d-9f41-3071b8813003'
INFO: sata0: dirty-bitmap status: created new
INFO: 5% (468.0 MiB of 8.0 GiB) in 3s, read: 156.0 MiB/s, write: 82.7 MiB/s
...

Is this by design or a bug?

 

[dcsapak]

kvm: -device ide-hd,bus=ahci0.0,drive=drive-sata0,id=sata0,rotation_rate=1,bootindex=100: Block node is read-only

this looks weird? the device is 'ide-hd' but mentions sata0?
can you post the output of 'pveversion -v' and the vm config ? (qm config ID) ?

edit: ignore what i said about ide, this is normal qemu stuff... the configs are interesting nonetheless

 

[fabian]

https://bugzilla.proxmox.com/show_bug.cgi?id=2862

 

[TReinhard]

This is the config:

agent: 1
balloon: 384
bootdisk: sata0
cores: 2
cpu: host
ide2: none,media=cdrom
memory: 1024
name: xxx
net0: virtio=5E1:58:32:71:3B,bridge=vmbr0,tag=30
numa: 0
ostype: other
sata0: rbd:base-104-disk-0,discard=on,size=8G,ssd=1
scsihw: virtio-scsi-pci
smbios1: uuid=1ed4ebf0-9bbb-49fb-ab81-ac4dd4b6a2d6
sockets: 1
vmgenid: 997e7d62-546a-4a98-bfe2-b1482a481a34
template: 1

And this this output of 'pveversion -v'

proxmox-ve: 6.3-1 (running kernel: 5.4.106-1-pve)
pve-manager: 6.3-6 (running version: 6.3-6/2184247e)
pve-kernel-5.4: 6.3-8
pve-kernel-helper: 6.3-8
pve-kernel-5.4.106-1-pve: 5.4.106-1
pve-kernel-5.4.65-1-pve: 5.4.65-1
ceph: 14.2.19-pve1
ceph-fuse: 14.2.19-pve1
corosync: 3.1.0-pve1
criu: 3.11-3
glusterfs-client: 5.5-3
ifupdown: 0.8.35+pve1
libjs-extjs: 6.0.1-10
libknet1: 1.20-pve1
libproxmox-acme-perl: 1.0.8
libproxmox-backup-qemu0: 1.0.3-1
libpve-access-control: 6.1-3
libpve-apiclient-perl: 3.1-3
libpve-common-perl: 6.3-5
libpve-guest-common-perl: 3.1-5
libpve-http-server-perl: 3.1-1
libpve-storage-perl: 6.3-8
libqb0: 1.0.5-1
libspice-server1: 0.14.2-4~pve6+1
lvm2: 2.03.02-pve4
lxc-pve: 4.0.6-2
lxcfs: 4.0.6-pve1
novnc-pve: 1.1.0-1
openvswitch-switch: 2.12.3-1
proxmox-backup-client: 1.0.13-1
proxmox-mini-journalreader: 1.1-1
proxmox-widget-toolkit: 2.4-9
pve-cluster: 6.2-1
pve-container: 3.3-4
pve-docs: 6.3-1
pve-edk2-firmware: 2.20200531-1
pve-firewall: 4.1-3
pve-firmware: 3.2-2
pve-ha-manager: 3.1-1
pve-i18n: 2.3-1
pve-qemu-kvm: 5.2.0-5
pve-xtermjs: 4.7.0-3
qemu-server: 6.3-10
smartmontools: 7.2-pve2
spiceterm: 3.1-1
vncterm: 1.6-2
zfsutils-linux: 2.0.4-pve1

 

[TReinhard]

This error seems to come from QEMU and the SATA driver: Looks like this driver wants write-access to the source-image, but Proxmox define them as read-only when backing up templates.

I'm not going to dig into QEMU-Source so this is my workaround:

--- /usr/share/perl5/PVE/QemuServer.pm~ 2021-03-30 18:40:58.000000000 +0200
+++ /usr/share/perl5/PVE/QemuServer.pm 2021-04-26 12:22:05.521247922 +0200
@@ -3590,7 +3590,7 @@
}

my $drive_cmd = print_drive_commandline_full($storecfg, $vmid, $drive);
- $drive_cmd .= ',readonly' if PVE::QemuConfig->is_template($conf);
+ #$drive_cmd .= ',readonly' if PVE::QemuConfig->is_template($conf);

push @$devices, '-drive',$drive_cmd;
push @$devices, '-device', print_drivedevice_full(

 

[fabian]

other workarounds would be:
- create instance based on template, backup instance
- switch to virtio-scsi

 

[fabian]

This error seems to come from QEMU and the SATA driver: Looks like this driver wants write-access to the source-image, but Proxmox define them as read-only when backing up templates.

I'm not going to dig into QEMU-Source so this is my workaround:

FWIW, I just sent a patch with a similar workaround (limited to skipping the readonly flag for SATA and IDE), which should fix the out-of-the-box experience while we evaluate whether another solution works better in the long-term.

https://lists.proxmox.com/pipermail/pve-devel/2021-April/047935.html