Arch Linux

jfabernathy

Member

From: North Carolina

Registered: 2019-01-03

Posts: 123

Install with mixture of btrfs and ext4 partitions

I have a new install with 1 nvme drive with 4 partitions: efi, swap, root(btrfs), /virtual(ext4)

When I created the system originally, I created all 4 partitions but didn't do anything with the ext4 partition.  I only have 2 subvols, @ and @home. 

After the install I created the /virtual directory  and mounted the ext4 partition on /virtual.  I then used KVM/virt-manager to create an use VMs directing the VM drive to /virtual to improve performance since VM drives and COW feature of btrfs is not optimal. 

So far so good, but adding the mount for /virtual in fstab created a system that failed at boot.  So obviously I did that wrong.  Here is my current fstab with the line for /virtual commented out so I can boot the system. 

 # /dev/nvme0n1p3
UUID=7d36553f-315a-4c86-9905-52c6020fa258       /               btrfs           rw,noatime,compress=zstd:3,ssd,space_cache=v2,subvolid=256,subvol=/@  0 0

# /dev/nvme0n1p1
UUID=7646-9E32          /boot           vfat            rw,relatime,fmask=0022,dmask=0022,codepage=437,iocharset=ascii,shortname=mixed,utf8,errors=remount-ro 0 2

# /dev/nvme0n1p3
UUID=7d36553f-315a-4c86-9905-52c6020fa258       /home           btrfs           rw,noatime,compress=zstd:3,ssd,space_cache=v2,subvolid=257,subvol=/@home      0 0

# /dev/nvme0n1p2
UUID=c933fb99-1633-4c82-adc8-048ea2b75d6a       none            swap            defaults        0 0
#
# /dev/nvme0n1p4 
# UID=85bbe3e4-580d-4d65-9de6-8f6ba9f34424      /virtual        ext4            defaults        0 0

I'm hoping someone can spot my mistake.

Head_on_a_Stick

Member

From: The Wirral

Registered: 2014-02-20

Posts: 8,813

Website

Re: Install with mixture of btrfs and ext4 partitions

# UID=85bbe3e4-580d-4d65-9de6-8f6ba9f34424      /virtual        ext4            defaults        0 0

Shouldn't that be "UUID"? Looks like you missed a "U".

Also:

COW feature of btrfs is not optimal

Disable that with

# chattr +C /virtual

See also https://wiki.archlinux.org/title/Btrfs# … rite_(CoW)

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Jin, Jîyan, Azadî

jfabernathy

Member

From: North Carolina

Registered: 2019-01-03

Posts: 123

Re: Install with mixture of btrfs and ext4 partitions

Thanks, it was a typo. I need new glasses :-)

I was going to test the performance of a separate ext4 partition versus disabling COW on a btrfs partition for the directory /virtual. At least now I can do the first part of the test.