Free space left

Free space left

[Michael Niederle]

How can I detect how much free space is left on a btrfs-volume?

As I read (and learned in practice!) "df" reports cannot be trusted if used on
btrfs-volumes.

Greetings, Michael

Re: Free space left

[Goffredo Baroncelli]

On Saturday 16 January 2010, Michael Niederle wrote:
> How can I detect how much free space is left on a btrfs-volume?
> 
> As I read (and learned in practice!) "df" reports cannot be trusted if used 
on
> btrfs-volumes.

Try btrfs-show

$ btrfs-show
Label: bar  uuid: ec2918cd-ad47-4eac-9e85-5604b02fd922
        Total devices 1 FS bytes used 302.25MB
        devid    1 size 964.81MB used 614.50MB path /dev/sdc1

Label: debian-root  uuid: 6e2a647f-5da2-4bd0-a7d7-9b13d13a47cc
        Total devices 1 FS bytes used 23.52GB
        devid    1 size 232.11GB used 118.03GB path /dev/sdc3

Btrfs Btrfs v0.19


BR
G.Baroncelli


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Re: Free space left

[Dipl.-Ing. Michael Niederle]

Hi, Goffredo!

> Try btrfs-show

Thanks for your advice!

btrfs-show works but it displays a lot of error message for non-btrfs devices:

> btrfs-show
failed to read /dev/sdg
failed to read /dev/sdg1
failed to read /dev/sdg2
failed to read /dev/sdg3
failed to read /dev/sdg4
failed to read /dev/md1
failed to read /dev/fd0
failed to read /dev/fd0u1440
failed to read /dev/fd1
failed to read /dev/hda
failed to read /dev/hda1
failed to read /dev/hda10
failed to read /dev/hda11
failed to read /dev/hda12
...
failed to read /dev/sr0
failed to read /dev/sr1
failed to read /dev/sr2
failed to read /dev/sr3
...
Label: Alpha4  uuid: 63b82dad-ed81-41f4-910f-7b358ceb77ba
	Total devices 1 FS bytes used 11.81GB
	devid    1 size 20.01GB used 20.01GB path /dev/sda3

Btrfs v0.19-4-gab8fb4c

Even if I try

btrfs-show /dev/sda3

I get the same output.

Greetings, Michael

Re: Free space left

[Goffredo Baroncelli]

On Saturday 16 January 2010, you (Dipl.-Ing. Michael Niederle) wrote:
> Hi, Goffredo!
> 
> > Try btrfs-show
> 
> Thanks for your advice!
> 
> btrfs-show works but it displays a lot of error message for non-btrfs 
devices:
> 
> > btrfs-show
> failed to read /dev/sdg
> failed to read /dev/sdg1
> failed to read /dev/sdg2
> failed to read /dev/sdg3
> failed to read /dev/sdg4
> failed to read /dev/md1
> failed to read /dev/fd0
> failed to read /dev/fd0u1440
> failed to read /dev/fd1
> failed to read /dev/hda
> failed to read /dev/hda1
> failed to read /dev/hda10
> failed to read /dev/hda11
> failed to read /dev/hda12
> ...
> failed to read /dev/sr0
> failed to read /dev/sr1
> failed to read /dev/sr2
> failed to read /dev/sr3
> ...
> Label: Alpha4  uuid: 63b82dad-ed81-41f4-910f-7b358ceb77ba
> 	Total devices 1 FS bytes used 11.81GB
> 	devid    1 size 20.01GB used 20.01GB path /dev/sda3
> 
> Btrfs v0.19-4-gab8fb4c
> 
> Even if I try
> 
> btrfs-show /dev/sda3
> 
> I get the same output.
> 
> Greetings, Michael
> 
Yes they search in every block devices a btrfs file-system. It may be 
smarter/faster skipping the floppy and the cd-rom..

BR
G.Baroncelli

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gpg key@ keyserver.linux.it: Goffredo Baroncelli (ghigo) <kreijackATinwind.it>
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Re: Free space left

[Svein Erik Brostigen]

Goffredo Baroncelli wrote:
> Try btrfs-show
>   
Ok:

$ mount
/dev/sdc on /media/452f782b-738a-4699-abfa-588eecab07ea type btrfs 
(rw,nosuid,nodev,uhelper=devkit)

$ df
/dev/sdc              932G  6.7G  925G   1% 
/media/452f782b-738a-4699-abfa-588eecab07ea

$ btrfs-show
failed to read /dev/sdb1
failed to read /dev/sdc
failed to read /dev/sdb
failed to read /dev/sda5
failed to read /dev/sda1
failed to read /dev/sda6
failed to read /dev/sda2
failed to read /dev/sda
failed to read /dev/sr0
failed to read /dev/loop1
failed to read /dev/ram2
failed to read /dev/ram10
failed to read /dev/ram11
failed to read /dev/loop7
failed to read /dev/ram1
failed to read /dev/loop0
failed to read /dev/loop5
failed to read /dev/loop2
failed to read /dev/loop3
failed to read /dev/loop4
failed to read /dev/loop6
failed to read /dev/ram12
failed to read /dev/ram4
failed to read /dev/ram13
failed to read /dev/ram5
failed to read /dev/ram8
failed to read /dev/ram14
failed to read /dev/ram15
failed to read /dev/ram0
failed to read /dev/ram3
failed to read /dev/ram6
failed to read /dev/ram9
failed to read /dev/ram7
Btrfs Btrfs v0.19

The drive used is a Seagate FreeAgent 1Tb USB drive under Ubuntu 9.10

$ uname -a
Linux ebrostig-laptop 2.6.31-18-generic-pae #55-Ubuntu SMP Fri Jan 8 
16:13:23 UTC 2010 i686 GNU/Linux

Erik

Re: Free space left

[Goffredo Baroncelli]

On Saturday 16 January 2010, you (Svein Erik Brostigen) wrote:
> Goffredo Baroncelli wrote:
> > Try btrfs-show
> >   
> Ok:



> $ mount
> /dev/sdc on /media/452f782b-738a-4699-abfa-588eecab07ea type btrfs 
> (rw,nosuid,nodev,uhelper=devkit)
> 
> $ df
> /dev/sdc              932G  6.7G  925G   1% 
> /media/452f782b-738a-4699-abfa-588eecab07ea
> 
> $ btrfs-show
> failed to read /dev/sdb1
> failed to read /dev/sdc
^^^^^^^^^

It seems that you don't have the right to read /dev/sdc.

Retry as super user.
[...]
> Btrfs Btrfs v0.19
> 
> The drive used is a Seagate FreeAgent 1Tb USB drive under Ubuntu 9.10
> 
> $ uname -a
> Linux ebrostig-laptop 2.6.31-18-generic-pae #55-Ubuntu SMP Fri Jan 8 
> 16:13:23 UTC 2010 i686 GNU/Linux
> 
> Erik
> 
> 


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Re: Free space left

[Mathieu Chouquet-Stringer]

        Hello,

kreijack@gmail.com (Goffredo Baroncelli) writes:
> Try btrfs-show
> [...]

How do you read this then:

Label: none  uuid: 27fafa43-7ad0-4e8a-ada8-36f73ef8984c
        Total devices 2 FS bytes used 79.63GB
        devid    2 size 111.79GB used 111.01GB path /dev/sdb
        devid    1 size 111.79GB used 111.03GB path /dev/sda

I'm pretty sure I created this fs with -d raid1 -m raid1!  Speaking
of which, is there a way to read a FS configuration: how can I tell
this FS really uses raid1 for both data and metadata?

The used column is surprising: if it's a mirror why 111.01 and
111.03?  And why all the space is being used anyway: I mean what's
the difference between the 79.63GB and 111.0[13]?

And the output of df is confusing too:
/dev/sdb             234441648  83501968 150939680  36% /space

It's reporting twice the total space but I think I remember looking
it up and that should be fixed in a future kernel version.
-- 
Mathieu Chouquet-Stringer                           mchouque@free.fr
            The sun itself sees not till heaven clears.
	             -- William Shakespeare --

Re: Free space left

[Goffredo Baroncelli]

On Saturday 16 January 2010, Mathieu Chouquet-Stringer wrote:
>         Hello,
> 
> kreijack@gmail.com (Goffredo Baroncelli) writes:
> > Try btrfs-show
> > [...]
> 
> How do you read this then:
> 
> Label: none  uuid: 27fafa43-7ad0-4e8a-ada8-36f73ef8984c
>         Total devices 2 FS bytes used 79.63GB
>         devid    2 size 111.79GB used 111.01GB path /dev/sdb
>         devid    1 size 111.79GB used 111.03GB path /dev/sda
> 
> I'm pretty sure I created this fs with -d raid1 -m raid1!  Speaking
> of which, is there a way to read a FS configuration: how can I tell
> this FS really uses raid1 for both data and metadata?

Even tough the raid mode is set per filesystem, btrfs has (will have) the 
capability to set the raid level per file. So it is no simple to estimate the 
free space: if every file is raid1 the real free space is half of the physical 
free space. But if some file are in raid1 (for examples /etc) and others are 
in raid0 (for example the ones under /usr which may be re-downloaded) the used 
space and the free space are difficult to estimate.

There are some efforts to fix this kind of situation (see the thread "[PATCH] 
Btrfs-progs: add btrfsctl -i to print space info").

> The used column is surprising: if it's a mirror why 111.01 and
> 111.03?  And why all the space is being used anyway: I mean what's
> the difference between the 79.63GB and 111.0[13]?
> 
> And the output of df is confusing too:
> /dev/sdb             234441648  83501968 150939680  36% /space
> 
> It's reporting twice the total space but I think I remember looking
> it up and that should be fixed in a future kernel version.
> -- 
> Mathieu Chouquet-Stringer                           mchouque@free.fr
>             The sun itself sees not till heaven clears.
> 	             -- William Shakespeare --
> 


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Key fingerprint = 4769 7E51 5293 D36C 814E  C054 BF04 F161 3DC5 0512