Size of vmdk-File in DatastoreBrowser not the same as in busybox?

[francwalter]

Hello,

i have some VMs in ESXi 4.0 U1, i installed the virtual Disks as "thin" so they should grow in size, when the VM is becoming bigger.

If i look at the vmdk-files in the DatastoreBrowser of vSphere Client 4 this is the case and i have some 20 GB files for my Windows Server 2008 vmdk-files.

But if i look into the real file system by busybox (i use WinSCP or putty, and same with Trilead VMX) then each vmdk-flat has the maximal size of 100 GB (exactly 107 GB). The vmdk-file is named there .vmdk-flat and not .vmdk like in the DatastoreBrowser.

If i download the vmdk-file by DatastoreBrowser to a Windows machine i get as well a vmdk-flat with big size and not the size indicated in DatastoreBrowser.

Surprisingly all vmdk-flat-files together (seen in WinSCP or VMX) are bigger than the physical HDD (500 GB).

What is this?

Thank you, franc

[DSTAVERT]

A vmdk actually consists of two files. A descriptor file and a data file. The descriptor file is simply a text file that includes a brief description of the disk and a pointer to the data file. The descriptor file on the disk would be something like server.vmdk and the data file would be server-flat.vmdk. When you view the files with the datastore browser the vSphere Client displays the server.vmdk but uses the on disk size of the server-flat.vmdk. When you look at the storage from the busybox console you will see allocated space (potential size).

[marcelo_soares]

This is the normal behavior. The VMDK is compressed on the VMFS level, so the real information is the one showed on the datastore browser. When you download the file, they will be copied with its uncompressed data.

Marcelo Soares

VMWare Certified Professional 310/410

Technical Support Engineer

Globant Argentina

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[DSTAVERT]

Beware when you over allocate storage. Snapshots and swapfiles can eat up space very quickly. have a look at Understanding Snapshots.

[Borja_Mari · Accepted solution]

Hi,

as marcelo said, the thin disks works at VMFS partition level. Thin disks doesn't exist outside a VMFS partition.

For example is you run "df -kh" you will see the real disk space usage (allocated) of the VMFS partition. In other words you are seeing the total amount of disk space used by the vms' thin disks.

Anyway, is you run in the busybox "ls -sh" (instead of "ls -lh") you will see the real disk space usage of the thin virtual disk of a particular vm (vmdk).

But the problem is that tools like winscp don't see the allocated disk size of the thin disks. This tools sees the reserved vmdk's file size. Then it copies all the disk file size as thick disks. And of course, the target file-system partition that will hold the thin disks, doesn't support thin disks.

A thin disk with 3 GB of real data (allocated) and a reserverd size of 10 GB is copied over the net by Winscp as a 10 GB disk.

Regards/Saludos,

Pablo

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[francwalter]

Now i know better, thank you.

Yours, franc