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ZFS TDEV friendly or hostile
Hi all knowledgeable persons...
I'm wondering if any one can say if ZFS is TDEV friendly or hostile, what I mean is... how will ZFS act together with tdev regarding thin device utilization. I'm 100% that VxFS 5.x will handle this really good in 5875 Enginuity , and is is already tdev aware in V-MAX 5874 Enginuity.
My belief is that ZFS will write it's data to unused space and the result is that it will eventually have allocated the total size of the tdev eliminating the thin device advantage!
Do any one else have this concern regarding ZFS and tdev's in a V-MAX environment?
/Lars
Lars4_bf562a
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October 9th, 2010 02:00
Well I think I have found my answer to the question- > And the answer is that ZFS is not going to take advantage of thin/dynamic provisioning.
As I also see it is that over time ZFS will create a random read behavior as ZFS writes is built on COW. So e.g. and Database of any kind that over time will update it's tables will result in block that are spread "all over the place" and add to that scenario a Datawarehose application depending on bandwidth.... maybe that's why ZFS and Solaris has the capability to have really large read cache on internal SSD.....
Reference material:
http://developers.sun.com/solaris/docs/wp-oraclezfsconfig-0510_ds_ac2.pdf
--- cut ---
A storage array that uses dynamic provisioning software to implement
virtual spare allocation is not recommended for Oracle Solaris ZFS. When
Oracle Solaris ZFS writes the modified data to free space, it rapidly writes
to the entire LUN volume, even with only a small percentage of used
space. The Oracle Solaris ZFS write process allocates all the virtual space
from the storage array's point of view, which negates the benefit of
dynamic provisioning.
--- paste ---
/Lars
vforde
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March 9th, 2011 15:00
Thanks for this Lars! Very useful