Talk:UseCases

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Regarding "ZFS does not need file system entries in /etc/vfstab", the point is that when a ZFS filesystem is created, it is immediately mounted and is automatically mounted on system startup. No fstab entry is needed for this. Same for subvolumes of the filesystem. The mount point is stored as an attribute of the volume. Even with this, the mount point of a subvolume on one filesystem (B) can also fall within a path existing on another filesystem (A).

On the same note: "ZFS does not need file system entries in /etc/fstab". Why is that such a good thing to have? Why would this be a dealbreaker? Brendan M. Hide 23:44, 30 October 2012 (UTC)


What is best practice when partitioning a device that holds one or more btr-filesystems

Both approaches are valid, depending what you are looking for.

  • Separate partitions and filesystem provide isolation. Problems with one filesystem remain with the data in that filesystem only (filesystem full, corruption, etc).
  • A single filesystem with subvolumes provide integration. You don't have to worry about growth in several filesystems as there is only one.

General wiki question: What is the etiquette about changes, discussion first, then move changes into the main page or should I just modify the main page directly, as I would on wikipedia ? User:Markus Nov 28 2014.


How do I label a filesystem?

The article currently indicates that labeling a multi-device filesystem is inadvisable. That information seems to be outdated according to the following:

IRC log:

[Ch4m3l30n]> I read that it's inadvisable to label a filesystem with more than one device. Is that still accurate?
<darkling> Not at all.
<darkling> It never was.
<[Ch4m3l30n]> https://btrfs.wiki.kernel.org/index.php/UseCases#How_do_I_label_a_filesystem.3F "the filesystem should not have more than one device"
<darkling> There were two threads from the same person who simply didn't get that he was labelling the filesystem, not the devices.
<darkling> Oh, that.
<darkling> That was a limitation of the tool. I think that's now no longer the case.

Command line output:

root@Chameleon:~# mkfs.btrfs -m raid1 -d raid1 /dev/sdc /dev/sdd /dev/sdb
WARNING! - Btrfs v3.12 IS EXPERIMENTAL
WARNING! - see http://btrfs.wiki.kernel.org before using
Turning ON incompat feature 'extref': increased hardlink limit per file to 65536
adding device /dev/sdd id 2
adding device /dev/sdb id 3
fs created label (null) on /dev/sdc
nodesize 16384 leafsize 16384 sectorsize 4096 size 6.82TiB
Btrfs v3.12
root@Chameleon:~# mount /dev/sdb /media/aux
root@Chameleon:~# mount | grep btrfs
/dev/sda2 on / type btrfs (rw,subvol=@)
/dev/sda2 on /home type btrfs (rw,subvol=@home)
/dev/sdc on /media/aux type btrfs (rw,nosuid,nodev,device=/dev/sdc,device=/dev/sdd,device=/dev/sdb)
root@Chameleon:~# btrfs filesystem show
Label: none uuid: f2a0beb1-37e9-443c-95a5-9f62add3fec1
Total devices 1 FS bytes used 901.96GiB
devid 1 size 931.33GiB used 908.04GiB path /dev/sda2
Label: none uuid: c3c6728a-5ecf-43b6-8bf7-229fe0a08332
Total devices 3 FS bytes used 640.00KiB
devid 1 size 2.73TiB used 2.02GiB path /dev/sdc
devid 2 size 2.73TiB used 1.01GiB path /dev/sdd
devid 3 size 1.36TiB used 1.01GiB path /dev/sdb
Btrfs v3.12
root@Chameleon:~# btrfs filesystem label /media/aux aux
root@Chameleon:~# btrfs fi show
Label: none uuid: f2a0beb1-37e9-443c-95a5-9f62add3fec1
Total devices 1 FS bytes used 901.96GiB
devid 1 size 931.33GiB used 908.04GiB path /dev/sda2
Label: aux uuid: c3c6728a-5ecf-43b6-8bf7-229fe0a08332
Total devices 3 FS bytes used 640.00KiB
devid 1 size 2.73TiB used 2.02GiB path /dev/sdc
devid 2 size 2.73TiB used 1.01GiB path /dev/sdd
devid 3 size 1.36TiB used 1.01GiB path /dev/sdb
Btrfs v3.12

Re: How do we implement quota in BTRFS?

# btrfs quota -> ERROR: Unknown command 'quota'

[ on Ubuntu 12.04.5 LTS, 3.13.0-57-generic, Btrfs v0.19, at least.]

-version specific, functionality moved, or missing a keyword between 'btrfs' and 'quota'? Bill S. (talk) 10:15, 29 July 2015 (UTC)

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