zfs discuss - Jan 2007 - using veritas dmp with ZFS (but not vxvm)

We have some HDS storage that isn''t supported by mpxio, so we have to
use veritas dmp to get multipathing.

Whats the recommended way to use DMP storage with ZFS. I want to use DMP but get
at the multipathed virtual luns at as low a level as possible to avoid using 
vxvm as much as possible.
I figure theres no point in having overhead from 2 volume manages if we can
avoid it.

Has anyone done this? Whats the best method?


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> We have some HDS storage that isn''t supported by mpxio, so we have
to
> use veritas dmp to get multipathing.
> Whats the recommended way to use DMP storage with ZFS. I want to use
> DMP but get at the multipathed virtual luns at as low a level as
> possible to avoid using vxvm as much as possible.
I think that means creating a VxVM volume, and then passing that volume
to zpool.  DMP doesn''t hand you a "device" that you can use.
> I figure theres no point in having overhead from 2 volume manages if
> we can avoid it.
Sure.  I don''t see an alternative for using DMP.  Given other reports
of
using ZFS on top of SVM metadevices, I wouldn''t expect peformance to
drop significantly.

Good luck.

--
Darren Dunham                                           ddunham@taos.com
Senior Technical Consultant         TAOS            http://www.taos.com/
Got some Dr Pepper?                           San Francisco, CA bay area
         < This line left intentionally blank to confuse you. >
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On Wed, 3 Jan 2007, Darren Dunham wrote:
>> We have some HDS storage that isn''t supported by mpxio, so we
have to
>> use veritas dmp to get multipathing.
>
>> Whats the recommended way to use DMP storage with ZFS. I want to use
>> DMP but get at the multipathed virtual luns at as low a level as
>> possible to avoid using vxvm as much as possible.
>
> I think that means creating a VxVM volume, and then passing that volume
> to zpool.  DMP doesn''t hand you a "device" that you can
use.
It does - but you cannot use it. The /dev/vx/dmp/ devices aren''t
working
properly, synchronization isn''t done within DMP but within VxVM.
There''s a
Veritas advisory and a SunAlert about _not_ putting filesystems directly
onto vxdmp devices because that causes data corruption on the buf(9S)
linkage fields and subsequent crashes/hangs. If you have access to
sunsolve.sun.com, see SunAlert 55980, or bug 4789779.
>
>> I figure theres no point in having overhead from 2 volume manages if
>> we can avoid it.
>
> Sure.  I don''t see an alternative for using DMP.  Given other
reports of
> using ZFS on top of SVM metadevices, I wouldn''t expect peformance
to
> drop significantly.
As said, should work, a plain vxvm volume on top of the vxdmp node, then
give that vxvm volume to ZFS.

FrankH.


>
> Good luck.
>
> --
> Darren Dunham                                           ddunham@taos.com
> Senior Technical Consultant         TAOS            http://www.taos.com/
> Got some Dr Pepper?                           San Francisco, CA bay area
>         < This line left intentionally blank to confuse you. >
> _______________________________________________
> zfs-discuss mailing list
> zfs-discuss@opensolaris.org
> http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
>
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