ZFS

How to use ZFS:

Background

There are three levels to understand

• zpools are a JBOD of one or more vdevs
• vdevs are groups of drives, likely in raidz (or raidz2, raidz3) or mirror.
• datasets are filesystems stored on a zpool, similar to partitions
• zvol is a virtual block device on a zpool without a filesystem

Usage

# Create a zpool with a mirror vdev.
zpool create -f -o ashift=12 -o compression=lz4 $zpool_name mirror \
  ata-diskA \
  ata-diskB

# Create a dataset.
zfs create -o encryption=aes-256-gcm -o keyformat=passphrase $zpool_name/$dataset_name

Notes

• You should always use the id under /dev/disk/by-id/
  • E.g. /dev/disk/by-id/ata-diskA

Alerts

First setup postfix to send emails.
Then setup ZED notifications

Automatic Scrubs

By default, ZFS on Ubuntu will automatically scrub every month

Automatic Snapshots

See sanoid

zfs list -t snapshot

Pros and Cons

VS Snapraid + btrfs + mergerfs

Pros

• ZFS has realtime parity.
• ZFS can work while degraded.
• ZFS snapshots with send and receive.
• ZFS has encryption on per-dataset.
• ZFS handles everything altogether including parity on permissions

Cons

• The main con is that ZFS is less expandable.
  • You can only expand by replacing every drive or adding entire vdevs.
• If many drives die, i.e. >2 for raidz2, you lose all your data.

Resources

• Arstechnica ZFS 101
• Archwiki: ZFS