zfs discuss - May 2009 - ZFS, difference in reported available space?

Hi.

Just to report the following.

Thanks for your time.

Regards.

****************************************

Forwarded conversation
Subject: Difference in reported available space?
------------------------

From: Rodrigo E. De Le?n Plicet <rdeleonp at gmail.com>
Date: Wed, May 27, 2009 at 1:00 PM
To: zfs-fuse at googlegroups.com

Sorry if the following is a dumb question.

Related to the attached file, I just want to understand why, if ''zpool
list'' reports 191MB available for coolpool, ''df -h|grep
cool'' only
shows 159MB available for coolpool?

Thanks for your time.

Regards.

----------
From: Rodrigo E. De Le?n Plicet <rdeleonp at gmail.com>
Date: Sat, May 30, 2009 at 8:51 PM
To: zfs-fuse at googlegroups.com

Anyone?

----------
From: Fajar A. Nugraha <fajar at fajar.net>
Date: Sun, May 31, 2009 at 5:34 AM
To: zfs-fuse at googlegroups.com

Possibly upstream bug.
http://markmail.org/message/zmygvaarfvseipzx

Better ask Sun folks, as it still happens on latest opensolaris
(2009.06) as well.

--
Fajar

****************************************
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root at localhost:/# uname -a
Linux newage 2.6.24-24-generic #1 SMP Wed Apr 15 15:54:25 UTC 2009 i686
GNU/Linux

root at localhost:/# zpool upgrade -v
This system is currently running ZFS pool version 13.

The following versions are supported:

VER  DESCRIPTION
---  --------------------------------------------------------
 1   Initial ZFS version
 2   Ditto blocks (replicated metadata)
 3   Hot spares and double parity RAID-Z
 4   zpool history
 5   Compression using the gzip algorithm
 6   bootfs pool property
 7   Separate intent log devices
 8   Delegated administration
 9   refquota and refreservation properties
 10  Cache devices
 11  Improved scrub performance
 12  Snapshot properties
 13  snapused property
For more information on a particular version, including supported releases, see:

http://www.opensolaris.org/os/community/zfs/version/N

Where ''N'' is the version number.

root at localhost:/# for i in 1 2 3 4; do dd if=/dev/zero of=disk$i bs=1024k
count=100; done

root at localhost:/# du -h disk*
101M    disk1
101M    disk2
101M    disk3
101M    disk4

root at localhost:/# zpool create coolpool mirror /disk1 /disk2

root at localhost:/# zpool add coolpool mirror /disk3 /disk4

root at localhost:/# zpool status
  pool: coolpool
 state: ONLINE
 scrub: none requested
config:

        NAME        STATE     READ WRITE CKSUM
        coolpool    ONLINE       0     0     0
          mirror    ONLINE       0     0     0
            /disk1  ONLINE       0     0     0
            /disk2  ONLINE       0     0     0
          mirror    ONLINE       0     0     0
            /disk3  ONLINE       0     0     0
            /disk4  ONLINE       0     0     0

errors: No known data errors

root at localhost:/# zpool list
NAME       SIZE   USED  AVAIL    CAP  HEALTH  ALTROOT
coolpool   191M    78K   191M     0%  ONLINE  -

root at localhost:/# df -h|grep cool
coolpool              159M   18K  159M   1% /coolpool

On Sun, May 31, 2009 at 10:29 AM, Rodrigo E. De Le?n Plicet <
rdeleonp at gmail.com> wrote:
> Hi.
>
> Just to report the following.
>
> Thanks for your time.
>
> Regards.
>
> ****************************************
>
> Forwarded conversation
> Subject: Difference in reported available space?
> ------------------------
>
> From: Rodrigo E. De Le?n Plicet <rdeleonp at gmail.com>
> Date: Wed, May 27, 2009 at 1:00 PM
> To: zfs-fuse at googlegroups.com
>
> Sorry if the following is a dumb question.
>
> Related to the attached file, I just want to understand why, if
''zpool
> list'' reports 191MB available for coolpool, ''df -h|grep
cool'' only
> shows 159MB available for coolpool?
>
> Thanks for your time.
>
> Regards.
>
> ----------
> From: Rodrigo E. De Le?n Plicet <rdeleonp at gmail.com>
> Date: Sat, May 30, 2009 at 8:51 PM
> To: zfs-fuse at googlegroups.com
>
> Anyone?
>
> ----------
> From: Fajar A. Nugraha <fajar at fajar.net>
> Date: Sun, May 31, 2009 at 5:34 AM
> To: zfs-fuse at googlegroups.com
>
> Possibly upstream bug.
> http://markmail.org/message/zmygvaarfvseipzx
>
> Better ask Sun folks, as it still happens on latest opensolaris
> (2009.06) as well.
>
> --
> Fajar
>
> ****************************************
>
>
That''s not a bug, and the behavior isn''t changing.  zpool list
shows the
size of the entire pool, including parity disks.  You cannot write user data
to parity disks/devices.  I suppose you could complain that the zpool list
command should account for user data as well as parity data being subtracted
from the entire pool, bug regardless, you shouldn''t be using zpool list
to
track your data usage as it doesn''t "hide" parity space like
the standard
userland utilities.

df shows the space available minus the parity device(s).

--Tim
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On Sun, May 31, 2009 at 12:57 PM, Tim<tim at tcsac.net>
wrote:
>
> On Sun, May 31, 2009 at 10:29 AM, Rodrigo E. De Le?n Plicet
> <rdeleonp at gmail.com> wrote:
>>
>> Related to the attached file, I just want to understand why, if
''zpool
>> list'' reports 191MB available for coolpool, ''df
-h|grep cool'' only
>> shows 159MB available for coolpool?
>
> That''s not a bug, and the behavior isn''t changing.? zpool
list shows the
> size of the entire pool, including parity disks.? You cannot write user
data
> to parity disks/devices.? I suppose you could complain that the zpool list
> command should account for user data as well as parity data being
subtracted
> from the entire pool, bug regardless, you shouldn''t be using zpool
list to
> track your data usage as it doesn''t "hide" parity space
like the standard
> userland utilities.
>
> df shows the space available minus the parity device(s).
But, in this case, I''m using mirroring. Wouldn''t the ZFS
parity
overhead apply to raidz/raidz2 only? I confess I''m not 100% clear on
the concepts...

Thanks for your time.

Regards.

Tim, Nevermind. I should have Read The Fine Manual (tm) from the start.

Says zpool(1M):
-------------------------------------------------------------------
(...)
zpool list (...)
(...)
This command reports actual physical space available to the storage
pool.  The physical space can be different from the total amount of
space that any contained datasets can actually use. The  amount  of
space  used in a raidz configuration depends on the characteristics
of the data being written. In addition, ZFS reserves some space for
internal  accounting  that  the zfs(1M) command takes into account,
but the zpool command does not. For non-full pools of a  reasonable
size,  these effects should be invisible. For small pools, or pools
that are close to being completely full,  these  discrepancies  may
become more noticeable.
(...)
-------------------------------------------------------------------

Thanks for your time.

Regards.