zfs discuss - Apr 2009 - ZFS volume -- special circumstances and usage in non-global zones

Hi,
The zfs(1M) man page indicates that a ZFS volume should only be used 
under special circumstances as below. 

            /*volume** */
                                    /A logical volume exported as a raw
                                    or block device. This type of
                                    dataset should only be used under
                                    special circumstances. File systems
                                    are typically used in most
                                    environments. Volumes cannot be used
                                    in a non-global zone./ 

However the ZFS administration guide 
<http://docs.sun.com/app/docs/doc/819-5461> seems to indicate that a ZFS 
volume can be used like any raw/ block device.  What are the special 
circumstances where we can not use a ZFS volume as a raw/ block device?

The administration guide also has an example on exporting a ZFS 
<http://docs.sun.com/app/docs/doc/819-5461/gbebi?a=view> volume to a zone.

    # *zonecfg -z zion*
    zion: No such zone configured
    Use ''create'' to begin configuring a new zone.
    zonecfg:zion> *create*
    zonecfg:zion> *add device*
    zonecfg:zion:device> *set match=/dev/zvol/dsk/tank/vol*
    zonecfg:zion:device> *end
    *

So why does the man page indicate that "Volumes cannot be used in a 
non-global zone".

Thanks
Ravi

*

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Hi,
The zfs(1M) man page indicates that a ZFS volume should only be used 
under special circumstances as below. 

            /*volume** */
                                    /A logical volume exported as a raw
                                    or block device. This type of
                                    dataset should only be used under
                                    special circumstances. File systems
                                    are typically used in most
                                    environments. Volumes cannot be used
                                    in a non-global zone./ 

However the ZFS administration guide 
<http://docs.sun.com/app/docs/doc/819-5461> seems to indicate that a ZFS 
volume can be used like any raw/ block device.  What are the special 
circumstances where we can NOT use a ZFS volume as a regular raw/ block 
device?

The administration guide also has an example on exporting a ZFS 
<http://docs.sun.com/app/docs/doc/819-5461/gbebi?a=view> volume to a zone.

    # *zonecfg -z zion*
    zion: No such zone configured
    Use ''create'' to begin configuring a new zone.
    zonecfg:zion> *create*
    zonecfg:zion> *add device*
    zonecfg:zion:device> *set match=/dev/zvol/dsk/tank/vol*
    zonecfg:zion:device> *end
    *

So why does the man page indicate that "Volumes cannot be used in a 
non-global zone".

Thanks
Ravi
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Hi Ravi,

I think a previous bug prevented the use of volumes in non-global zones
and the man page was not updated. This is a bug in the man page. I will
fix this.

I agree that this text here:

http://docsview.sfbay.sun.com/app/docs/doc/819-5461/ftyxh?a=view

A ZFS volume is a dataset that represents a block device and can be used 
like any block device.

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

Could be widely interpreted and should be revised to indicate when using 
a volume is appropriate.

Cindy
Ravi Kota wrote:
> Hi,
> The zfs(1M) man page indicates that a ZFS volume should only be used 
> under special circumstances as below. 
> 
>             /*volume** */
>                                     /A logical volume exported as a raw
>                                     or block device. This type of
>                                     dataset should only be used under
>                                     special circumstances. File systems
>                                     are typically used in most
>                                     environments. Volumes cannot be used
>                                     in a non-global zone./ 
> 
> However the ZFS administration guide 
> <http://docs.sun.com/app/docs/doc/819-5461> seems to indicate that a
ZFS
> volume can be used like any raw/ block device.  What are the special 
> circumstances where we can NOT use a ZFS volume as a regular raw/ block 
> device?
> 
> The administration guide also has an example on exporting a ZFS 
> <http://docs.sun.com/app/docs/doc/819-5461/gbebi?a=view> volume to a
zone.
> 
> # *zonecfg -z zion*
> zion: No such zone configured
> Use ''create'' to begin configuring a new zone.
> zonecfg:zion> *create*
> zonecfg:zion> *add device*
> zonecfg:zion:device> *set match=/dev/zvol/dsk/tank/vol*
> zonecfg:zion:device> *end
> *
> 
> So why does the man page indicate that "Volumes cannot be used in a 
> non-global zone".
> 
> Thanks
> Ravi
> 
> 
> ------------------------------------------------------------------------
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