zfs discuss - Oct 2010 - stripes of different size mirror groups

I have a couple drive enclosures:
15x 450gb 15krpm SAS
15x 600gb 15krpm SAS

I''d like to set them up like RAID10.  Previously, I was using two
hardware RAID10 volumes, with the 15th drive as a hot spare, in each enclosure.

Using ZFS, it could be nice to make them a single volume, so that I could share
L2ARC and ZIL devices, rather than buy two sets.

It appears possible to set up 7x450gb mirrored sets and 7x600gb mirrored sets in
the same volume, without losing capacity.  Is that a bad idea?  Is there a
problem with having different stripe sizes, like this?

Thanks,
    Rob
-- 
This message posted from opensolaris.org

On 10/29/10 09:40 AM, Rob Cohen wrote:
> I have a couple drive enclosures:
> 15x 450gb 15krpm SAS
> 15x 600gb 15krpm SAS
>
> I''d like to set them up like RAID10.  Previously, I was using two
hardware RAID10 volumes, with the 15th drive as a hot spare, in each enclosure.
>
> Using ZFS, it could be nice to make them a single volume, so that I could
share L2ARC and ZIL devices, rather than buy two sets.
>
> It appears possible to set up 7x450gb mirrored sets and 7x600gb mirrored
sets in the same volume, without losing capacity.  Is that a bad idea?  Is there
a problem with having different stripe sizes, like this?
>
>    
The problem would be one of performance once the pool becomes more than 
75% full.  At this point the smaller vedevs may be full and all new 
write activity will be restricted to the bigger devices.

-- 
Ian.

Thanks, Ian.

If I understand correctly, the performance would then drop to the same level as
if I set them up as separate volumes in the first place.

So, I get double the performance for 75% of my data, and equal performance for
25% of my data, and my L2ARC will adapt to my working set across both
enclosures.

That sounds like all upside, and no downside, unless I''m missing
something.

Are there any other problems?
-- 
This message posted from opensolaris.org

> If I understand correctly, the performance would then drop to the same
> level as if I set them up as separate volumes in the first place.
> 
> So, I get double the performance for 75% of my data, and equal
> performance for 25% of my data, and my L2ARC will adapt to my working
> set across both enclosures.
> 
> That sounds like all upside, and no downside, unless I''m missing
> something.
> 
> Are there any other problems?
Not really. You also have the option to replace the smaller drives with bigger
ones, one by one, if you set autogrow=on on that pool.

Vennlige hilsener / Best regards

roy
--
Roy Sigurd Karlsbakk
(+47) 97542685
roy at karlsbakk.net
http://blogg.karlsbakk.net/
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