Resizing a btrfs managed partition

Resizing a btrfs managed partition

[planetf1]

Hi,
  Let me know if this is the wrong place to ask...

  I'm using Fedora 12 x86_64, mostly with the newer 21.6.32 kernel, and 
have a single btrfs filesystem within a 120Gb partition.

  I'd like to extend the space btrfs can use. One option is presumably 
add a new device to btrfs, but I was hoping to simple resize the 
existing partition to say 160Gb.

  With ext4 I might do this with gparted , although mostly I'd use LVM, 
with seperate LVs for /opt /home / etc and that's been the way I've done 
it for many years.

  With btrfs I'm unsure as to the safe steps and decided to skip on use 
of LVM giving the enhanced capabilities of btrfs itself.

  Is it ok to resize the partition with gparted?
  How do I make btrfs use the new partition size?
  Or are there other btrfs specific tools that can manage partitions
  Would I be better off still using lvm in conjunction with btrfs?
  Are there good pointers to useful user material on btrfs on these issues?
  Is creating new subvolumes to manage /home (say I want to limit that 
space, and create snapshots independently) appropriate, and if so what's 
the easiest way to do that -- I had trouble with getting the subvolume 
ops to work

Mostly rather than NEED btrfs per se, I'm using a clean laptop 
environment as a way to experiment with the new filesystem & understand 
how to manage it.

Thanks
Nigel.
bugs@cherrybyte.me.uk

Re: Resizing a btrfs managed partition

[Goffredo Baroncelli]

On Wednesday 24 February 2010, planetf1 wrote:
> Hi,
Hi

>   Let me know if this is the wrong place to ask...
> 
>   I'm using Fedora 12 x86_64, mostly with the newer 21.6.32 kernel, and 
> have a single btrfs filesystem within a 120Gb partition.
> 
>   I'd like to extend the space btrfs can use. One option is presumably 
> add a new device to btrfs, but I was hoping to simple resize the 
> existing partition to say 160Gb.
> 
>   With ext4 I might do this with gparted , although mostly I'd use LVM, 
> with seperate LVs for /opt /home / etc and that's been the way I've done 
> it for many years.
> 
>   With btrfs I'm unsure as to the safe steps and decided to skip on use 
> of LVM giving the enhanced capabilities of btrfs itself.
> 
>   Is it ok to resize the partition with gparted?
IIRC gparted want to resize both partition and filesystem. So if gparted 
doesn't support btrfs, it will not be usable
>   How do I make btrfs use the new partition size?
I am never tried, but it should be sufficient to 
a) resize the underling partition (with fdisk)
b) resize the filesystem (with btrfsctl -r <size> <path-to-filesystem>).

If you want to grow the filesystem, the step are a) then b). Otherwise if you 
want to shrink the filesystem the step are b) then a)

Pay attention to:
- btrfs support online filesystem
- if you resize a partition it may be required to reboot the system, otherwise 
the kernel may not be able to read the new size of the partition
- if you pass 'max' as size of the btrfsctl utility, the filesystem grows up 
to fill all available space.

I suggest you to test the resizing on a loop device before tring a real 
filesystem.

>   Or are there other btrfs specific tools that can manage partitions
Not in my knowledge 
>   Would I be better off still using lvm in conjunction with btrfs?
In theory btrfs has the capability to add/remove device and resize a 
filesystem. But it is a young filesystem, so the results may be not the one 
expected.
>   Are there good pointers to useful user material on btrfs on these issues?
http://btrfs.wiki.kernel.org/index.php
http://btrfs.wiki.kernel.org/index.php/Using_Btrfs_with_Multiple_Devices

>   Is creating new subvolumes to manage /home (say I want to limit that 
> space, and create snapshots independently) appropriate, and if so what's 
> the easiest way to do that -- I had trouble with getting the subvolume 
> ops to work

If you don't use snapshot creating a subvolume is not useful. If you had 
problem, post the command which you had used.
 
> Mostly rather than NEED btrfs per se, I'm using a clean laptop 
> environment as a way to experiment with the new filesystem & understand 
> how to manage it.
> 
> Thanks
> Nigel.
> bugs@cherrybyte.me.uk
>
BR
Goffredo
> 
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Re: Resizing a btrfs managed partition

[planetf1]

On 02/24/2010 05:58 PM, Goffredo Baroncelli wrote:

> a) resize the underling partition (with fdisk)
> b) resize the filesystem (with btrfsctl -r<size>  <path-to-filesystem>).

Thanks for the reply. These steps worked fine :-) Just got used to using 
gparted for many years rather than carefully writing down cylinder 
start/end numbers ....