[DRBD-user] DRBD and LVM Snapshots

Michael Hierweck michael at hierweck.de
Sun May 14 18:11:35 CEST 2017

Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.

Hi all,

up to now to use LVM (thick) provisioning to provide virtual disks for
VMs: RAID => LVM => LV => DRBD => KVM/QEMU (virtio).

We would like to be able to take snapshots from our virtual disks in
order to be able to use them as readonly source to consistent backups.
Therefore we would need to introduce a LVM thin provisioning layer

A. TP below DRBD
RAID => LVM => LVM-TP => LV => DRBD => KVM/QEMU (virtio)

- simple setup
- I suppose going back to an older snapshost would this break DRBD and
require a complete resync/verify run

B. TP on top of DRBD
RAID => LVM => LV => DRBD => LVM => LVM-TP => LV => KVM/QEMU (virtio)
- complex setup
- more layers affect reliability and performance
- snapshots are replicated and consistent
- additional diskspace for snaphosts is limited by the DRBD volume size
an connot be shared across volumes.

I would like to discuss the pros and the cons of both approaches while
considering internal vs. external metadata.

Thanks in advance


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