LVM and snapshot-as-volume-chain

[FingerlessGloves]

Hi,

I've created a 3 node Proxmox cluster to test, and presented a Fibre Channel Lun. I've then created a LVM group on top as per https://pve.proxmox.com/wiki/Multipath

I then imported a VM, and it's done raw format on the lvm storage group. I couldn't create a snapshot, so I reimported the disk as qcow2 on the LVM storage, and I can now create a snapshot.

Is that the correct image type to use for getting snapshots on Shared LVM storage?
https://pve.proxmox.com/wiki/Storage:_LVM#pvesm_lvm_config

Is there any performance impact to using qcow2 in the LVM group or is it's not quite the same as using a qcow2 file on say ext4?


```
# lvs
LV VG Attr LSize
vm-100-disk-0 virt-test-1 -wi-ao---- 32.00g
vm-103-disk-0.qcow2 virt-test-1 -wi------- <32.01g
```

 

[bbgeek17]

Is that the correct image type to use for getting snapshots on Shared LVM storage?

yes, that is the correct type. Once you enable the Snapshot-as-volume-chain, the format will be QCOW on LVM.
Keep in mind that this technology is in Preview mode.

Is there any performance impact to using qcow2 in the LVM group or is it's not quite the same as using a qcow2 file on say ext4?

There is an associated performance impact to using QCOW whether on LVM or on top of a filesystem. There is additional processing required when snapshots are involved. Whether it will be perceivable (affect your workflow) depends on what that workflow and its requirements are.

These articles may be helpful to get started:
https://kb.blockbridge.com/technote/proxmox-qcow-snapshots-on-lvm
https://kb.blockbridge.com/technote/proxmox-qemu-cache-none-qcow2

---

Blockbridge : Ultra low latency all-NVME shared storage for Proxmox - https://www.blockbridge.com/proxmox

 

[FingerlessGloves]

yes, that is the correct type. Once you enable the Snapshot-as-volume-chain, the format will be QCOW on LVM.
Keep in mind that this technology is in Preview mode.


There is an associated performance impact to using QCOW whether on LVM or on top of a filesystem. There is additional processing required when snapshots are involved. Whether it will be perceivable (affect your workflow) depends on what that workflow and its requirements are.

These articles may be helpful to get started:
https://kb.blockbridge.com/technote/proxmox-qcow-snapshots-on-lvm
https://kb.blockbridge.com/technote/proxmox-qemu-cache-none-qcow2

---

Blockbridge : Ultra low latency all-NVME shared storage for Proxmox - https://www.blockbridge.com/proxmox

Thanks for those useful links, I'll read those tomorrow, when I'm back in work