Last month Itzik Reich, CTO at EMC, posted on his blog and twitter about the importance of automated space reclamation and how – until VMware comes up with a solution on its own – Raxco’s “PerfectStorage is a MUST if you want to utilize [sic] every bit of space.”
If you haven’t already, it’s time for you to look at @RaxcoSoftware ,their perfectstorage is a MUST if you want to utlize every bit of space
— Itzik Reich (@itzikr) April 30, 2014
Reich points out in his blog that physical capacity doesn’t return to the storage array after deleting files from within the guest OS or outside of the VM, such as deleting an actual VM from the datastore. The guest OS must translate the UNMAP command to the parental hypervisor or OS and the parental hypervisor must pass this information to the underlying storage array.
How to Automatically – and Efficiently – Reclaim Space
Storage arrays are expensive and the ability to reclaim GBs and TBs of storage space can mean thousands of dollars in savings until data legitimately grows to the point you have to purchase more hardware. But until then, why waste your budget on something that can simply be reclaimed – and automated?
“Back in the vSphere 5.0 era, VMware DID support an automated UNMAP command but it turned out that in rare circumstances, it actually caused [sic] data corruption so you now need to do it manually at both the in-guest level and the datastore level.”
Currently, to reclaim space to be able to use it again, you must run a utility like sDelete on every VM. Once the sDelete command finishes its run, your physical capacity increases — but the datastore must be made aware of the reclaimed space in order to use it.
In vSphere 5.1, Reich explains:
“Run the vmfstools –y command, it will create a balloon file that will then get deleted and release the capacity back to the array”
For vSphere 5.5, basically the same process is employed, except you would now run the UNMAP command.
But there is still the issue of needing to manually run sDelete on hundreds or thousands of VMs. Reich found a smart, efficient, automated alternative to doing just that:
“Well, there is some hope, you can use a third party tool, which ain’t free like sDelete, but will automate, report and consume the capacity for you, the software I was using is from a company called RAXCO and the specific product is “PerfectStorage.””
Reich shares a screenshot from a VDI lab running 2,500 VDI VMs and persistent desktops. He uses Login VSI to generate load on it so temporary windows files do exist. In this screenshot, PerfectStorage reports he can reclaim 5.14TB of space.
Reich also explains how easy it is to deploy PerfectStorage:
“I used its ability to push the MSI package and it took me 2 minutes to configure the policy and around 2 hours to push it to 2,500 VMs.”
..and how efficient PerfectStorage is:
“The scanning capability is also very important because it lets YOU decide if you want to reclaim back the capacity or leave it as is and wait for the next scanning reporting, the actual claiming process is very sophisticated as it takes into an account both the guest OS / ESX CPU utilization so it knows to “behave” itself in a virtualized environment…they call it Virtualization Awareness, it takes into an account not just the kernel CPU and the user Mode CPU but also the Disk I/O, pretty cool in my (humble) opinion!”
Getting 4.6 Times More Storage
Reich is a happy PerfectStorage customer:
“After running either sDelete or RAXCO [PerfectStorage] and then running the datastore space reclaim commands on these two datastores, the data reduction has gone up to 4.6:1 !!! That is really good, it means you are buying an EMC XtremeIO array but you are getting X 4.6 of what you pay for..”
“…I truly hope that one day VMware will support SPARSE-SE as the default vdisk format but until then your best option is to use RAXCO PerfectStorage.”
This post has been updated on December 7, 2015 to reflect Reich’s promotion from Principal SE and Field CTO of EMC’s Emerging Technology Unit to CTO after the initial publication of this article.