Quantum Forum for DXi V5000

Where are the "Savings" ?

Just installed Vmpro in eval mode. Backed up five VM's directly from a single ESXi host.

The web interface says under the "Savings" column figures varying between 35% and 91%

But the VMDK backup files produced by Vmpro are all exactly the same size as the original VM's on the ESXi host.

Where are the "Savings", am I missing something?

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Permalink Reply by DoubleDensity on July 17, 2014 at 11:55am

Hi Adrian,

If you have the storage device type set to 'Quantum DXi' then you will enable sparse file creation. If you want to create files which occupy less space on the target disk then you want this enabled, even if you are not writing to a DXi. In this case the files created by vmPRO will have a logical size that is equivalent to the provisioned size of the VMDK disks, but the actual used bytes on disk will reflect only the active blocks which were copied over.

For example, due to the way that Windows handles and presents ‘sparse’ file utilization by default, it can look as if the files are taking up much more space than they actually are. In some cases you can even have files which appear to be larger than the total size of the drive, although the disk itself will not actually be full.

There is a tool available from SysInternals/MS TechNet which will show you the true size of these files on disk:

Windows DU command:

http://technet.microsoft.com/en-us/sysinternals/bb896651.aspx

For example if you are backing up to the E:\vmPRO directory on a Windows server, or are looking at a UNC mount (NetApp) you can run the command like this:

du -v E:\vmPRO

It will show you the ‘logical’ size, for example 34 GB that represents the full size of the VM, and then the ‘actual’ size on disk which should be much smaller -- note the difference, however in Windows Explorer you only ever see the logical ‘size’ value.

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Permalink Reply by Adrian Blazer on July 17, 2014 at 12:20pm

Hi DoubleDensity

Thanks for the fast reply! Great tip about the du tool, thanks too

I ran the backup with mostly all the default settings, and saved to FreeNAS Server.

The total size of all five VM's is 253Gb, after calculating the "savings" I should be left with 122Gb

So I ran that tool, and sure enough it shows:

size: 252,977,109,789 bytes

size on disk: 12,458,964,922 !!!!!

Can this really be true, 252Gb has become only about 12Gb of space on my NAS, staggering if true...

Where are the "Savings" ?

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