On Wed, 2014-03-12 at 19:22 -0600, Chris Murphy wrote:
On Mar 12, 2014, at 7:11 PM, Patrick O'Callaghan
<pocallaghan(a)gmail.com> wrote:
> (Sorry for the subject line but it's the best I could come up with)
>
> I recently installed F20 on a new system with a 120GB SSD and 1TB hard
> drive. I'm using the SSD for /, /boot, /var and swap, and the hard drive
> for /home. I decided to live on the edge and partition /home as BTRFS.
> All this was done from Anaconda with no subsequent changes except adding
> a few labels.
>
> This is what I find:
>
> $ lsblk --fs
> NAME FSTYPE LABEL UUID
MOUNTPOINT
> sda
> ├─sda1 ext4 boot
6d5929d8-fd35-49e6-a8bf-aab5309dad77 /boot
> ├─sda2 btrfs fedora_pxeclient-arch-00000-undi-002001-d4-3d-7e-f4-1b-08
22fecad3-619d-4a9b-aace-35a2e4e04c49 /home
> ├─sda3 ext4 root
6a9a800c-309b-4b69-b269-884ad495e7b9 /
> ├─sda4
> ├─sda5 ext4 var
d5955869-af07-4d6e-b1b3-6ccb31208b41 /var
> └─sda6 swap
1431e6d2-531e-46cd-8633-1cf878c6b2a1 [SWAP]
> sdb
> └─sdb1 btrfs fedora_pxeclient-arch-00000-undi-002001-d4-3d-7e-f4-1b-08
22fecad3-619d-4a9b-aace-35a2e4e04c49
>
> Note that /dev/sda2 and /dev/sdb1 have the same UUID and label.
I think you've stumbled into a bug. Since Btrfs directly supports multiple devices,
it's like LVM or raid in this respect, and for LVM and RAID, anaconda might be eager
to configure multiple device layouts this way.
So I'm going to bet dollars to donuts this is a Btrfs raid0 volume. What do you get
for
btrfs fi df /home #this is short for btrfs filesystem df /home
$ sudo btrfs fi df /home
Data, single: total=78.01GiB, used=73.44GiB
System, RAID1: total=8.00MiB, used=16.00KiB
System, single: total=4.00MiB, used=0.00
Metadata, RAID1: total=1.00GiB, used=295.20Mi
Metadata, single: total=8.00MiB, used=0.00
I'm wondering where the bulk of the 1TB HDD has gone.
> $ df -h
> Filesystem Size Used Avail Use% Mounted on
> /dev/sda3 68G 8.5G 56G 14% /
> devtmpfs 7.8G 0 7.8G 0% /dev
> tmpfs 7.9G 5.6M 7.8G 1% /dev/shm
> tmpfs 7.9G 1.1M 7.9G 1% /run
> tmpfs 7.9G 0 7.9G 0% /sys/fs/cgroup
> tmpfs 7.9G 72K 7.9G 1% /tmp
> /dev/sda1 477M 113M 335M 26% /boot
> /dev/sda5 27G 1.8G 24G 7% /var
> /dev/sda2 932G 73G 858G 8% /home
>
> Note that /dev/sda2 is mounted and /dev/sdb1 is not. However /dev/sda2
> has around 1TB of space, so it's clearly the hard drive.
Yeah the multiple device mounting behavior is different. You can mount either device and
the entire volume is thus mounted, you don't have to be explicit as btrfs finds its
other parts and uses them; it only complains when it can't find them.
OK
> What's going on, and should I be worried?
Well, it's raid0 so yeah I'd make a backup of anything important. It is possible
to do an online conversion to a single device layout, but depending on what you have in
/home it might actually be easier to back it up, blow away the current btrfs partitions,
and redo the mkfs on just sdb1, add the new UUID to your fstab, mount the new /home and
restore from backup. But I leave that up to you. The conversion is straight forward and it
should work, I've done it a bunch of times but you know… "yay btrfs with crossed
fingers".
It appears to be RAID1 from the above.
>
> Also, how can I change the label of the BTRFS partition? I used the
> "btrfs filesystem label ..." command but although it registers the
> change, the existing fedora_pxeclient.... label still shows up
> in /dev/disk/by-label.
What do you get for
btrfs fi show
$ sudo btrfs fi show
Label: xtra uuid: 22fecad3-619d-4a9b-aace-35a2e4e04c49
Total devices 2 FS bytes used 73.72GiB
devid 1 size 4.19GiB used 1.03GiB path /dev/sda2
devid 2 size 927.32GiB used 79.01GiB path /dev/sdb1
And does the first line Label: match the new label or the old?
xtra is the new label. /dev/disk/by-label still shows the old label and
not the new one.
poc