Understanding DF, etc.

Understanding DF, etc.

[Swâmi Petaramesh]

Hi list,

I have trouble understanding this, which doesn't really correspond to
the wiki FAQ (so my question is hopefully not a FAQ ;-) :

# btrfs fi df /
Data: total=74.01GB, used=72.77GB
System, DUP: total=8.00MB, used=16.00KB
System: total=4.00MB, used=0.00
Metadata, DUP: total=1.75GB, used=657.48MB
Metadata: total=8.00MB, used=0.00

Some questions are :

What are the "DUP" lines compared to the "non-DUP" ones ?

If I can understand "Metadata" and "Data", what is "System" supposed to
be ?

Is there anyway to know how much space is consumed by any given
subvolume or snapshots (for snapshots, "du" cannot tell how much they
really consume, of course...)

This is so clear in ZFS for example ;-) ...and such a mystery in
BTRFS...

I also have a question relating to quotas : I understand that
per-subvolume quotas are not (yet ?) implemented, but is it possible to
use the user quotas system with btrfs, i.e. mounting it with the "quota"
option such as ol'ext2/3 did ?

TIA, kind regards.

Re: Understanding DF, etc.

[Helmut Hullen]

Hallo, Sw=E2mi,

Du meintest am 13.05.11:

> I have trouble understanding this, which doesn't really correspond to
> the wiki FAQ (so my question is hopefully not a FAQ ;-) :

> # btrfs fi df /
> Data: total=3D74.01GB, used=3D72.77GB
> System, DUP: total=3D8.00MB, used=3D16.00KB
> System: total=3D4.00MB, used=3D0.00
> Metadata, DUP: total=3D1.75GB, used=3D657.48MB
> Metadata: total=3D8.00MB, used=3D0.00

> Some questions are :

> What are the "DUP" lines compared to the "non-DUP" ones ?

That may depend on the "mkfs.btrfs" options - which options have you =20
set?

What tells

        df -t btrfs

        btrfs filesystem show

Viele Gruesse!
Helmut
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Re: Understanding DF, etc.

[Swâmi Petaramesh]

Hi Helmut,

Le vendredi 13 mai 2011 =C3=A0 21:50 +0200, Helmut Hullen a =C3=A9crit =
:
> That may depend on the "mkfs.btrfs" options - which options have you =
=20
> set?

Well, actually none, except for -L ;-)

> What tells
>         df -t btrfs
>         btrfs filesystem show=20

root@tethys:~# df -t btrfs
Sys. de fichiers           1K-blocs   Utilis=C3=A9    Dispo. Uti% Mont=C3=
=A9 sur
/dev/mapper/VG1-TETHYS
                     152735744  78383976  71999272  53% /
/dev/mapper/VG1-TETHYS
                     152735744  78383976  71999272  53% /tmp
/dev/mapper/VG1-TETHYS
                     152735744  78383976  71999272  53% /home
/dev/mapper/VG1-TETHYS
                     152735744  78383976  71999272  53% /var
/dev/sda2               392192     26772    193660  13% /boot

root@tethys:~# btrfs filesystem show
failed to read /dev/sr0
Label: 'TETHYS_BOOT'  uuid: b6b9e7ef-5aae-4c49-8b5a-39d6eec1d7d7
	Total devices 1 FS bytes used 25.76MB
	devid    1 size 383.00MB used 240.50MB path /dev/sda2

Label: 'TETHYS'  uuid: 82c61fc2-8f8c-4cce-9d0d-ed446f671062
	Total devices 1 FS bytes used 74.11GB
	devid    1 size 145.66GB used 77.54GB path /dev/dm-1

Btrfs Btrfs v0.19


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Re: Understanding DF, etc.

[Helmut Hullen]

Hallo, Sw=E2mi,

Du meintest am 14.05.11:

>>> # btrfs fi df /
>>> Data: total=3D74.01GB, used=3D72.77GB
>>> System, DUP: total=3D8.00MB, used=3D16.00KB
>>> System: total=3D4.00MB, used=3D0.00
>>> Metadata, DUP: total=3D1.75GB, used=3D657.48MB
>>> Metadata: total=3D8.00MB, used=3D0.00

>>         btrfs filesystem show

> root@tethys:~# df -t btrfs
> Sys. de fichiers           1K-blocs   Utilis=E9    Dispo. Uti% Mont=E9
> sur /dev/mapper/VG1-TETHYS
>                      152735744  78383976  71999272  53% /
> /dev/mapper/VG1-TETHYS
>                      152735744  78383976  71999272  53% /tmp
> /dev/mapper/VG1-TETHYS
>                      152735744  78383976  71999272  53% /home
> /dev/mapper/VG1-TETHYS
>                      152735744  78383976  71999272  53% /var
> /dev/sda2               392192     26772    193660  13% /boot

> root@tethys:~# btrfs filesystem show
> failed to read /dev/sr0
> Label: 'TETHYS_BOOT'  uuid: b6b9e7ef-5aae-4c49-8b5a-39d6eec1d7d7
> 	Total devices 1 FS bytes used 25.76MB
> 	devid    1 size 383.00MB used 240.50MB path /dev/sda2

> Label: 'TETHYS'  uuid: 82c61fc2-8f8c-4cce-9d0d-ed446f671062
> 	Total devices 1 FS bytes used 74.11GB
> 	devid    1 size 145.66GB used 77.54GB path /dev/dm-1


Ok - just for your information the messages of my system, created with

   mkfs.btrfs -d raid0 -m raid1 ...

# btrfs filesystem show
Label: 'MMedia'  uuid: 120b036a-883f-46aa-bd9a-cb6a1897c8d2
	Total devices 3 FS bytes used 1.68TB
	devid    2 size 1.81TB used 603.02GB path /dev/sdb1
	devid    1 size 1.82TB used 599.51GB path /dev/sde1
	devid    3 size 1.81TB used 603.01GB path /dev/sdc1

Btrfs Btrfs v0.19

# btrfs filesystem df /srv/MM
Data, RAID0: total=3D1.75TB, used=3D1.67TB
System, RAID1: total=3D16.00MB, used=3D116.00KB
System: total=3D4.00MB, used=3D0.00
Metadata, RAID1: total=3D4.25GB, used=3D2.53GB

# df -t btrfs
=46ilesystem    Type   1K-blocks      Used Available Use% Mounted on
/dev/sdb1    btrfs   5846053400 1803934240 2718410984  40% /srv/MM

----------------------------------------

I don't know what's the meaning of the type "DUP" (instead of "RAID0" o=
r =20
"RAID1" in my example).

In your case "btrfs filesystem df" seems to show something about specia=
l =20
informations and their need of space but nothing about used space or =20
available space.

Some weeks ago there has been a thread about the informations of "df", =
=20
"btrfs filesystem df" and "btrfs filesystem show"; most times there may=
 =20
be shown the "at least available space".


Viele Gruesse!
Helmut
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Re: Understanding DF, etc.

[Swâmi Petaramesh]

Le dimanche 15 mai 2011 =C3=A0 19:28 +0200, Helmut Hullen a =C3=A9crit =
:
> shows that that device with brutto 150 GByte is nearly full with its
> 78 GByte (or 73 GByte) data because it uses this kind of RAID1?=20

No. Here's the current situation on same machine :

# btrfs fi df /
Data: total=3D85.01GB, used=3D84.56GB
System, DUP: total=3D8.00MB, used=3D16.00KB
System: total=3D4.00MB, used=3D0.00
Metadata, DUP: total=3D1.75GB, used=3D1.01GB
Metadata: total=3D8.00MB, used=3D0.00

As far as I understood, only metadata (not data) are DUPed, and the DAT=
A
zone is allocated as needed by 1GB chunks. So I currently use 84.5 GB
and the system has thus allocated 85 GB of filesystem DATA space. When
they get full, the system will allocate 1 more GB, etc. Until the devic=
e
itself gets full, of course.

You notice here that there's no indication about the device actual size
(this df gives developper-useful data, not sysadmin-useful data ;-)) bu=
t
this file system resides in :=20

# mount
/dev/mapper/VG1-TETHYS on / type btrfs
(rw,relatime,subvol=3DUBUNTU,compress=3Dzlib)
[...]

# lvs VG1/TETHYS
  LV     VG   Attr   LSize   Origin Snap%  Move Log Copy%  Convert
  TETHYS VG1  -wi-ao 145,66g



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Re: Understanding DF, etc.

[Helmut Hullen]

Hallo, Hugo,

Du meintest am 15.05.11:

>>>>> # btrfs fi df /
>>>>> Data: total=3D74.01GB, used=3D72.77GB
>>>>> System, DUP: total=3D8.00MB, used=3D16.00KB
>>>>> System: total=3D4.00MB, used=3D0.00
>>>>> Metadata, DUP: total=3D1.75GB, used=3D657.48MB
>>>>> Metadata: total=3D8.00MB, used=3D0.00

>> I don't know what's the meaning of the type "DUP" (instead of
>> "RAID0" or "RAID1" in my example).

>    DUP is a form of RAID-1 for single disks. Like RAID-1, it stores
> two copies of the data, but where RAID-1 guarantees that the two
> copies will be on different devices, DUP stores both copies on the
> same device. btrfs uses DUP by default for metadata on single-device
> filesystems, so that if part of the FS metadata is damaged (by, say,
> unrecoverable bad blocks), there's still a good copy.

>    If you add another disk to the filesystem and balance, the DUP
> chunks are automatically converted to RAID-1.

Sounds very interesting!

In this special case: does that mean that

> root@tethys:~# df -t btrfs
> Sys. de fichiers           1K-blocs   Utilis=E9    Dispo. Uti% Mont=E9
> sur /dev/mapper/VG1-TETHYS
>                      152735744  78383976  71999272  53% /
> /dev/mapper/VG1-TETHYS
>                      152735744  78383976  71999272  53% /tmp

shows that that device with brutto 150 GByte is nearly full with its 78=
 =20
GByte (or 73 GByte) data because it uses this kind of RAID1?

Viele Gruesse!
Helmut
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