On Dec 30, 2009, at 12:25 PM, Andras Spitzer wrote:
Richard,
That's an interesting question, if it's worth it or not. I guess the
question is always who are the targets for ZFS (I assume everyone,
though in reality priorities has to set up as the developer
resources are limited). For a home office, no doubt thin
provisioning is not much of a use, for an enterprise company the
numbers might really make a difference if we look at the space used
vs space allocated.
There are some studies that thin provisioning can reduce physical
space used up to 30%, which is huge. (Even though I understands
studies are not real life and thin provisioning is not viable in
every environment)
Btw, I would like to discuss scenarios where though we have over-
subscribed pool in the SAN (meaning the overall allocated space to
the systems is more than the physical space in the pool) with proper
monitoring and proactive physical drive adds we won't let any
systems/applications attached to the SAN realize that we have thin
devices.
Actually that's why I believe configuring thin devices without
periodically reclaiming space is just a timebomb, though if you have
the option to periodically reclaim space, you can maintain the pool
in the SAN in a really efficient way. That's why I found Veritas'
Thin Reclamation API as a milestone in the thin device field.
Anyway, only future can tell if thin provisioning will or won't be a
major feature in the storage world, though as I saw Veritas already
added this feature I was wondering if ZFS has it at least on it's
roadmap.
Thin provisioning is absolutely, positively a wonderful, good thing!
The question
is, how does the industry handle the multitude of thin provisioning
models, each
layered on top of another? For example, here at the ranch I use VMWare
and Xen,
which thinly provision virtual disks. I do this over iSCSI to a server
running ZFS
which thinly provisions the iSCSI target. If I had a virtual RAID
array, I would
probably use that, too. Personally, I think being thinner closer to
the application
wins over being thinner closer to dumb storage devices (disk drives).
BTW, I do not see an RFE for this on http://bugs.opensolaris.org
Would you be so kind as to file one?
-- richard
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