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Manjaro ZFS Setup

Wednesday, 08 Jul 2020 18:38:00 · 4 minute read
Linux / desktop / · computing /

At the end of my last post I noted that I’d switched from an Ubuntu flavoured distro to Manjaro Linux. I’ve been rocking it for over a month now, first on an 2013 Dell Optiplex 9090 but it just got an upgrade!

It’s the first build I’ve done in a long time, and the first AMD build I’ve done. The old Dell had a couple of hard drives I mirrored with ZFS, but this new machine has a slightly more elaborate setup:

In this post I’m documenting how the disks are configured.

Solid State Drives

Partition Layout

Number  Start   End     Size    File system     Name                         Flags
 1      1049kB  1075MB  1074MB  fat32           ssd-top-S1CUNYADC10187-boot  boot, esp
 2      1075MB  3222MB  2147MB  linux-swap(v1)  ssd-top-S1CUNYADC10187-swap  swap
 3      3222MB  218GB   215GB                   ssd-top-S1CUNYADC10187-zfs

You can see each partition gets a label stating that it’s an SSD, where it is in the case, the serial number, and what the partition is for.

Boot

Currently the boot partition is a vfat file system containing the required bits for systemd-boot. It’s not currently mirrored and this post will get updated when I figure that bit out.

SWAP

I created a mirror of the two SSDs second partitions using mdadm, issued mkswap and told the system to start using it.

[adref ~]# mdadm --create swap --level=1 --raid-devices=2 --metadata=0.90 /dev/disk/by-partlabel/ssd-top-S1CUNYADC10187-swap /dev/disk/by-partlabel/ssd-bottom-SA400S37-swap
[adref ~]# mkswap /dev/md/swap
mkswap: /dev/md/swap: warning: wiping old swap signature.
Setting up swapspace version 1, size = 2 GiB (2147414016 bytes)
no label, UUID=97e5dbc0-3d26-4ae3-8bac-95561feee566
[adref ~]# swapon /dev/disk/by-uuid/97e5dbc0-3d26-4ae3-8bac-95561feee566

I also copied it to /etc/fstab - see end.

Operating System

I really like the ZFS layout that FreeBSD uses. It was a while ago and I can’t recall how Manjaro sets ZFS datasets up, but I didn’t like it, so I used the following create my OS disk:

zpool create -o ashift=12 -m none zroot mirror /dev/disk/by-partlabel/bottom-Z4S68HRV-zfs /dev/disk/by-partlabel/top-Z4S47V4C-zfs
zpool export zroot
zpool import -R /mnt zroot
zfs create -o mountpoint=none zroot/ROOT
zfs create -o mountpoint=/ zroot/ROOT/default
zfs set compression=on zroot
zfs set atime=off zroot
zfs create -o mountpoint=/tmp -o exec=on -o setuid=off zroot/tmp
zfs create -o mountpoint=/usr -o canmount=off zroot/usr
zfs create -o mountpoint=/home zroot/home
zfs create -o mountpoint=/var -o canmount=off -o xattr=sa zroot/var
zfs create -o atime=on zroot/var/mail
zfs create -o exec=on -o setuid=off zroot/var/tmp
zfs create zroot/var/cache
zfs create zroot/var/cache/pacman
zfs create -o canmount=off -o mountpoint=/var/lib zroot/var/lib
zfs create zroot/var/lib/docker
zfs create zroot/var/lib/libvirt
zfs create -o canmount=off -o mountpoint=/var/lib/systemd zroot/var/lib/systemd
zfs create zroot/var/lib/systemd/coredump
zfs create zroot/var/log
zfs create zroot/var/log/journal
zpool set bootfs=zroot/ROOT/default zroot

Note: The above uses the two home directory drives, I’ve since copied these to the SSDs but I’ve not changed the disk names in the above to match the new setup.

Home Directory Drives

Partition Layout

Number  Start   End     Size    File system  Name              Flags
 3      3222MB  2000GB  1997GB               top-Z4S47V4C-zfs

Spot the oddity? This drive starts around 3GB in because I used to have /boot and SWAP partitions on here before they migrated to the SSDs.

ZFS

ZFS is a little complicated because I’ve removed the OS datasets from this pool and kept my home directory, but itI’ve done something like this:

zpool create -o ashift=12 -m none pwll mirror /dev/disk/by-partlabel/bottom-Z4S68HRV-zfs /dev/disk
/by-partlabel/top-Z4S47V4C-zfs
zfs create pwll/home
zfs set mountpoint=/home pwll/home
zfs create pwll/home/bil

I’ve got more datasets under my home directory that came from another machine.

Note: pwll is Welsh for ‘pool’.

Backup Drive

The backup drive used to be my Time Machine drive on my Mac. It has a basic partition layout:

Number  Start   End     Size    File system  Name  Flags
 1      1049kB  2000GB  2000GB

It’s got a single dataset:

zpool create tad /dev/disk/by-id/ata-MB2000GCWLT_PDJ71PUX-part1

And I just zfs send snapshot to it periodically.

Note: tad is Sindarin Elvish for ’two'.

Useful bits

SSD Partitioning

The below was used to create the required partitions on the boot drive.

[adref ~]# sgdisk -n1:0:+1G -t1:ef00 /dev/sdc
The operation has completed successfully.
[adref ~]# sgdisk -n2:0:+2G -t2:8200 /dev/sdc
The operation has completed successfully.
[adref ~]# sgdisk -n3:0:+200G -t3:bf00 /dev/sdc
The operation has completed successfully.

[adref ~]# parted /dev/sdc
GNU Parted 3.3
Using /dev/sdc
Welcome to GNU Parted! Type 'help' to view a list of commands.
(parted) name 1 ssd-bottom-SB400S37-boot                                  
(parted) name 2 ssd-bottom-SB400S37-swap
(parted) name 3 ssd-bottom-SB400S37-zfs
(parted) print                                                            
Model: ATA KINGSTON SA400S3 (scsi)
Disk /dev/sdc: 240GB
Sector size (logical/physical): 512B/512B
Partition Table: gpt
Disk Flags: 

Number  Start   End     Size    File system  Name                      Flags
 1      1049kB  1075MB  1074MB               ssd-bottom-SB400S37-boot  boot, esp
 2      1075MB  3222MB  2147MB               ssd-bottom-SB400S37-swap  swap
 3      3222MB  218GB   215GB                ssd-bottom-SB400S37-zfs

(parted) quit                                                             
[adref ~]#

fstab

# /dev/sda1 UUID=B38A-1CFD
/dev/disk/by-partlabel/ssd-top-S1CUNYADC10187-boot	/boot     	vfat      	rw,relatime,fmask=0022,dmask=0022,codepage=437,iocharset=iso8859-1,shortname=mixed,utf8,errors=remount-ro	0 0

# /dev/md/swap 97e5dbc0-3d26-4ae3-8bac-95561feee566
UUID=97e5dbc0-3d26-4ae3-8bac-95561feee566	none      	swap      	defaults,pri=-2	0 0
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