StoreVirtual Storage
cancel
Showing results for 
Search instead for 
Did you mean: 

Reclaiming Space from a thin provisioned netword raid-5 volume

 
SOLVED
Go to solution
Anthony B Hall
Occasional Visitor

Reclaiming Space from a thin provisioned netword raid-5 volume

We have Windows 2003 Enterprise connected to a large 30 TB volume and are trying to shrink the volume by moving files from it into a smaller volume i.e. eventually deleting the files from the large volume. I had expected the space to be returned once the snapshot had processed. What do I have to do to recover this space ? Would the result have been different if I had thick provisioned the storage ?

thanks in advance,

Anthony.
84 REPLIES 84
Highlighted
teledata
Respected Contributor
Solution

Re: Reclaiming Space from a thin provisioned netword raid-5 volume

This is always one of the challenges (and limitations) to thin provisioning.

The technology used to provide thin provisioning in SAN/iQ is really more of a "high water mark".

Once a block has been marked as "written" you cannot recover unused space by deleting data from the volume. There is no communication facility in which the OS would "tell" the SAN that,
"Hey that block of data we were using yesterday, is now empty and you can have it back."

Since there is no way to "tell" the SAN the space is empty, those blocks of data, once written to cannot be reclaimed.

Your only option is to create a NEW volume, and migrate the data to the new volume, and then delete the old volume.

This can be challenging with direct native iSCSI mounted volumes, but if you are using a virtual machine (with virtual disks) you can reclaim storage by creating a new VMFS datastore, using sdelete to zero out unused space (within the Windows OS), then performing a storage migration and choosing "thin" provisioning on the virtual disk.

While still requiring a new (VMFS) volume, the virtualized disk can be left intact avoiding any reconfiguration within the Windows server itself.


The result would NOT be different if you had chosen thick vs thin. The blocks are still marked as used and a "high water mark" is still maintained. The only difference is when you mark it "thick" SAN/iQ reserves the entire space, and it cannot be used to provision to other volumes/snapshots.

This is why you can dynamically switch between thin and thick provisioning within the CMC.

http://www.tdonline.com
Matthew D
Frequent Advisor

Re: Reclaiming Space from a thin provisioned netword raid-5 volume

teledata - I'm curious, is this still the case with VAAI and 9.0?  I was under the impression that vSphere + VAAI + 9.0 would allow block zeroing and reclaim free space when VM's were destroyed.  I really have no clue - couldn't find any definitive information out there about it.

Jitun
Trusted Contributor

Re: Reclaiming Space from a thin provisioned netword raid-5 volume

Matthew for now space reclamation is not supported by LeftHand OS.
But we can expect that in the future releases.
I work for HPE
--------------------------------------------------------------
How to assign points? Click the KUDOS! star!
oikjn
Honored Contributor

Re: Reclaiming Space from a thin provisioned netword raid-5 volume

matthew, you are correct, VAAI supports space reclaimation and there are new SCSI commands that support this feature, but as Jitun said, StoreVirtual doesn't support this feature yet so we are S.O.L. until they decide to.

 

This feature was "comming soon" along with SMI-S support since 9.5.  Its 10.5 now and nobody from HP has said anything about those features ETA.

 

IMO, "We can expect that in the future release" is a pretty good statement in that these are now more considered basic features and if HP isn't going to include them in future releases this product line is dead and I"m sure we all hope that isn't the case.

Patrick Neuner
Regular Advisor

Re: Reclaiming Space from a thin provisioned netword raid-5 volume

Its 2014 - but still no change when talking about this behaviour. On Linux with Mysql Databases and Dumps, this is also a huge problem. A Volume with 170 GB but a LUN that has 500 GB assigned, it will take weeks, until 500 GB is used up. For Hosting Business and sales very bad - as thin provisioning on good storage is a must to be able to make good pricing. 

 

Also Remote Replication is a hazzle this way, we transfer about 300 GB of data for those 170 GB, where less than 10 GB change. With Rsync it would save lots of bandwidth, but it's not a snapshot then. 

 

We also heard from support - it will be in a future release. But that was with OS 10.0. Now we had 10.5, 11, not sure what future release they mean, I hope 11.5 and not 20. Otherwise our Lefthand will be out of warranty in 1 year - we will switch to another system. I like the Lefthand approach though, but price compared to features a no go. 

 

I still believe they don't add this feature to sell 3PAR, or - because they know, once the feature is active, lot's of people don't need to extend existing lefthands as suddenly lots of free space is available. 

 

Anyway - this feature should not be promoted as it's not a real thin provisioning, we found out the hard way - after purchase. 

 

Patrick

Bart_Heungens
Honored Contributor

Re: Reclaiming Space from a thin provisioned netword raid-5 volume

Hi,

 

Cannot tell you anything in detail but 2014 will be a good year! ;-)

 

 

Kr,

Bart

--------------------------------------------------------------------------------
If my post was useful, clik on my KUDOS! "White Star" !
Gediminas Vilutis
Frequent Advisor

Re: Reclaiming Space from a thin provisioned netword raid-5 volume


@Bart_Heungens wrote:

Hi,

 

Cannot tell you anything in detail but 2014 will be a good year! ;-)

 

 

Kr,

Bart


And after missing Nth deadline for LH OS v11 online upgrades, do you expect us to believe into these nice HP roadmaps? :)

 

I've seen T10 unmap promises probably for 2 years already. As always, it is somewhere 'not in next release, but after that...'. Unfortunately, when next LH OS release is out, roadmaps also get shifted :(

 

 

oikjn
Honored Contributor

Re: Reclaiming Space from a thin provisioned netword raid-5 volume

lol. Ged you are so right.
Bart_Heungens
Honored Contributor

Re: Reclaiming Space from a thin provisioned netword raid-5 volume

Same question the other way around:

Why do you want online update to 11.0?

Biggest change in 11.0 is Adaptive Optimization.

Your current physical appliances are not capable to use this feature, only the new 4335 appliance, besides the new VSA 2014.

So why is everyone asking for online update of appliances that cannot use the new features?

 

And yes the code is ready, there is only an issue found in 1 particular update case with 1 particular G2 model with 10Gb interface. And HP prefers to release the code which is 100% perfect in all cases... I follow them in their opinion...

--------------------------------------------------------------------------------
If my post was useful, clik on my KUDOS! "White Star" !