zfs discuss - Dec 2010 - A couple of quick questions

1) What''s the maximum number of disk devices that can be used to
construct filesystems?

2) Is there a practical limit on #1? I''ve seen messages where folks
suggested 40 physical devices is the practical maximum. That would seem to imply
a maximum single volume size of 80TB...

3) Are vdevs hierarchical? e.g. can I construct multiple vdevs of physical
drives, then construct filesystems by stacking/aggregating those vdevs together?

Thanks,

P.
-- 
This message posted from opensolaris.org

I can''t answer any of these authoritatively(?), but have a comment:

On Wed, Dec 22, 2010 at 10:55, Per Hojmark <xscribe at gmail.com>
wrote:
> 1) What''s the maximum number of disk devices that can be used to
construct filesystems?
lots.
> 2) Is there a practical limit on #1? I''ve seen messages where
folks suggested 40 physical devices is the practical maximum. That would seem to
imply a maximum single volume size of 80TB...
how does that follow, or, in other words, why do you believe zfs can
only handle 2 TB per physical disc? (hint: look up GTP or EFI label
;-)

HTH
-- 
regards/mit freundlichen Gr?ssen
Michael Schuster

Hi Per,

Disk devices are used to create ZFS storage pools. Then, you create file 
systems that can access all the available disk space in the storage
pool. ZFS file systems are not constrained to any physical disk in the
storage pool.

Consider that you will need to backup your data regardless of the size
of storage pool so you are constrained by the practical limits of what
you can actually manage. Be realistic.

Yes, you can create multiple virtual devices of physical drives, but
you can''t stack those vdevs on top of each other.

See the ZFS best practices guide for other recommendations:

http://www.solarisinternals.com/wiki/index.php/ZFS_Best_Practices_Guide

No real practical limits:

http://hub.opensolaris.org/bin/view/Community+Group+zfs/whatis

Thanks,

Cindy

On 12/22/10 02:55, Per Hojmark wrote:
> 1) What''s the maximum number of disk devices that can be used to
construct filesystems?
> 
> 2) Is there a practical limit on #1? I''ve seen messages where
folks suggested 40 physical devices is the practical maximum. That would seem to
imply a maximum single volume size of 80TB...
> 
> 3) Are vdevs hierarchical? e.g. can I construct multiple vdevs of physical
drives, then construct filesystems by stacking/aggregating those vdevs together?
> 
> Thanks,
> 
> P.