2011-07-09 04:00 PM
I'm wondering if there is support for TRIM/Discard in Ontap with operating systems that has the abillity to use that feature.
What I mean is OS like Win2K8 R2/newer Linux/ FreeBSD/ MacOS X etc being able to reclaim unused blocks in thin provisioned LUNs.
Also, from what rumors claim Vmware will support the same when vSphere 5 is released (in a few days?) making LUNs storage almost as dynamic as NFS shares regarding allocation.
I know Snapdrive for Windows can do this since a while, but last time I checked it this wasn't the same thing as TRIM/Discard and only scheduled instead of immediatly.
I can't find other reference to the same feature on Netapp, an not on the disk side either thinking of it (for SSD disk support due to performance reasons).
2011-07-12 05:47 AM
You can use the Space Reclaimer from within SnapDrive to accomplish the same objective.
And with LUNs you still have the same problem that any free space that you get in the volume (regardless of what triggers it: TRIM, Deduplication, ...) is not immediately available to ESX and you have to use LUN overcommitment to effectively use that free space.
BTW I think it will take a bit more than "a few days" for vSphere 5 to be released. Last time I heard they were talking about a March 2010 release or, somwhere around March
2011-07-12 11:19 AM
The rumors were true and Vmware just announced vSphere 5 including the new VMFS5 with SCSI UNMAP support, exactly the feature I'm asking about.
For some insight check out this blog : http://virtualgeek.typepad.com/virtual_geek/2011/07/vstorage-apis-for-array-integration-vaai-vsphere-5-edition.html
Now, as Vmware is a big player, and Netapp added Vmware VAAI support just a few months after if was announced I would guess that any new coderelease will include support for the new vSphere features.
I would find it quite unfortunate if the same technology (scsi unmap) wouldn't be presented to LUNs connected to Windows 2008 R2/Linux/etc physical servers as it is exactly the same SCSI command being sent down the pipe.
One thing still missing in the new vSphere is the abillity to pass thru any "scsi unmap" from within the virtual machines. This would ultimately make LUNs as dynamic as I would like them to be.
TW – there’s one important thing that TODAY vSphere 5 doesn’t do – thin provisioning commands are not “punched through” the virtual disk layer. This means that if a guest issued a SCSI UNMAP command to a virtual SCSI device, it wouldn’t result in a space reclaim at the array level – only vmkernel level space reclaim works. This is something you can count on in the future (and there may be interesting ways to do it before then, hint hint).
2011-09-15 06:18 PM
I wrote a driver a while back for the Mac that does space reclaimation on NetApp LUNs. It hooks into TRIM support in the storage stack in Snow Leopard and Lion. I only got to test it with iSCSI but it should work fine with FC as well.
2011-09-22 04:02 PM
netapp answered the question on scsi unmap thru a blog today: