Which Filesystem for Linux Guests on ZFS Storage?


Active Member
Jun 24, 2019
Which filesystem shoud I choose for a Linux guest?

I am running various Linux guests on Proxmox 6 with a ZFS Storage. The storage is usually configured as either mirror or raidz2, both with compression "on". The guest storage is usually set to SCSI on VirtIO SCSI controller with "discard" enables, aka. thin provisioning.

Depending on the Linux flavor of the guest, different filesystems are the default:
  1. ext4 (with or without LVM) on Debian/Ubuntu
  2. XFS on CentoOS
  3. btrfs on OpenSuse
  4. ZFS usually not a default, but supported by many.
just to name a few.

Despite the default setting, many Linux flavors would also support other filesystems, e.g., ext3/4 is supported by nearly everyone. But which one to choose?
Just a clarification: I do not want to discuss different features supported by each FS. For what most guests VMs are used for, the exact filesystem used does not matter in terms of features. I am only interested in the interaction between guest FS and the ZFS underlay.

How will each interact with ZFS? Bandwidth penality? IOPS penality?
Are some better than others?
Do I have to "align" blocksizes of guest FS with ZFS?
Is it a big deal that ZFS compression is enabled?


BTRFS over zfs will be bad for performance(COW over another COW). For the rest xfs/ext4 is OK. I prefer ext4 because I can also shrink it if I need a smaller partion!

Good luck / Bafta !
Last edited:
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ext4 (with or without LVM) on Debian/Ubuntu

Nowadays, I omit the installation with LVM. I use one small virtual disk with one partition with ext4 and create another virtual disk if I need a data disk inside. This works great with newer linux distributions where partprobe works correctly. I see no benefit in using LVM here. If you want to use LVM, I suggest you use the physical disk as physical volume omitting the partition, because this is another additional step for resize operations.
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