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by luzer7 814 days ago
Does anyone have a good _basic_ guide on LVM/LVM Thin? I'm having a hard time wrapping my head around LVM and moving the vmdk to it. Mainly a Window admin with some Linux experience.

I understand that LVM holds data in it but when I make a Windows VM in proxmox it stores the data in a LVM partition(?) as opposed to ESXi or Hyper-V making a VHD or VMDK.

Kinda confusing .
2 comments
abbbi 814 days ago
proxmox is using LVM for direct attached raw volumes. LVM is just a logical volume manager for linux, which gives you more features than using old fashioned disk partitioning. I guess they chose this path for windows virtual machine migration because windows running on vmware before, does usually not have the required virtio drivers installed to support the qemu hypervisors virtio solution for disk bus virtualization out of the box. It would mean the hypervisor has to simulate IDE or SCSI bus which comes with great overhead perfomance wise (in the case of migration)

So an direct attached lvm volume is the best solution performance wise. In the vmware world this would be an direct attached raw device either from local disk or SAN.

For fresh install on proxmox its better to chose qcow as disk image format with virtio-scsi bus (comparable to vhdx, vmdk, qemus disk format) and add virtio drivers during windows setup.

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m463 814 days ago
i ran into the same sort of documentation desert.

off the top of my head:

- keep in mind there is LVM and LVM2, and proxmox now uses lvm2

- I don't understand the thinpool allocation. You don't have to use lvm-thin if you don't want to deal with oversubscribed volumes, or don't care about snapshots or cloning storage.

- get to know "pvesm". A lot of things you can do in the gui

- when making linux VMs, I found it easier to use separate devices for the efi partition and the linux partition, such as:

  efidisk0: local-lvm:vm-205-disk-0,size=4M
  virtio0: local-lvm:vm-205-disk-1,iothread=1,size=1G
  virtio1: local-lvm:vm-205-disk-2,cache=writeback,discard=on,iothread=1,size=32G
(virtio0 = efi, virtio1 = /)

and I can mount/expand/resize /dev/mapper/big2-vm--205--disk--2 without having to deal with disk partitions

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