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T10 unmap and 3Par Space reclaimation
https://3parug.net/viewtopic.php?f=18&t=340		 Page 1 of 1
Author:  gkapoor [ Thu Jun 13, 2013 4:49 am ]
Post subject:  T10 unmap and 3Par Space reclaimation
Hello All,

I am aware that in VmWare 5.0 U1 T10 unmap is disabled by default and I have been running vmkfstools to clean up the space, followed by compactcpg on 3par.

I have been hearing that in VmWare 5.0 Update 2, T10 unmap is working as expected but I don't see it in release notes of update 2.

Just wanted to check if anyone else out there is aware of this or is using VmWare 5.0 update 2 and aware if its really working well to reclaim space on its own provided all VV's are zero detect enabled.

Thanks,
G Kapoor
Author:  brettcarr [ Mon Jun 17, 2013 1:24 pm ]
Post subject:  Re: T10 unmap and 3Par Space reclaimation
I havent heard this and have spoken with VMWare about it on several occasions, what makes you think it has been turned back on?

Brett
Author:  rabievdm [ Fri Jun 21, 2013 7:02 am ]
Post subject:  Re: T10 unmap and 3Par Space reclaimation
Funny I was about to ask the forum if anyone is using the UNMAP command :)
We have a P7400 and ESXi5.1u1 and could not understand why space reclamation was not happening till I read this:
http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=2014849
As far as I can see VMware have disabled the command 'period' the impact on the backend storage was to unpredictable its now up to you the customer to enable it on all your hosts.
The question is how is it handled on the 3PAR, our test seems to suggest it's not a real-time process as the space does not reflect immediately once we delete a VM, also we ran test and could not really see an impact, but then again the unit was not in production at the time. It's now in production and we thought it best to ask around before enabling it.

So... has anyone out there enable it? (advanced/VMFS3.EnableBlockDelete=1)

PS I recently read that 'another' storage vender who's name I will not mention lest I soil this list :) has picked up an issue with the VMware UNMAP code that has issues when reclaiming more that 2TB BUT I think they are confused and have mixed UNMAP with a manual reclaim (vmkfstools) as I understood that UNMAP run in the background on a storage system:
http://cormachogan.com/2013/05/14/heads-up-unmap-considerations-when-reclaiming-more-than-2tb/
Author:  gkapoor [ Fri Jun 21, 2013 7:51 am ]
Post subject:  Re: T10 unmap and 3Par Space reclaimation
I believe even if you enable it it won't work. Not sure about 5.1U1 but I did enable the advance option Of SCSI unmap (VMFS3.EnableBlockDelete=1) in 5.0 U1 but it never worked.

However, I believe the blog you mentioned below talked about the issues with reclaiming space using vmkfstools where if you mention the percentage to reclaim is higher than 2TB results into errors because its trying to create a baloon file of that much sixe which comes after the calculation of percentage mentioned to reclaim and if that file gets bigger than 2TB, it could be an issue.

Thanks,
G Kapoor
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