Quick format in Microsoft OS in Thin VMDK format disk

[ferdis]

Hi,

VMware documentation mentions in document "Using thin provisioned disks with virtual machines"

this:

"In order for a guest operating system to make use of a virtual disk, the guest operating system must first partition and format the disk to a file system it can recognize. Depending on the type of format selected within the guest operating system, the format may cause the thin provisioned disk to grow to a full size.

For example, if you present a thin provisioned disk to a Microsoft Windows operating system and format the disk, unless you explicitly select the Quick Format option, the Microsoft Windows format tool writes information to all of the sectors on the disk, which in turn inflates the thin provisioned disk."

But when I tried to use quick format or normal format in Microsoft VM both in Thin disk format there is no difference in real size of vmdk on vmfs. Any ideas why?

Thanks.

Frantisek

[rickardnobel]

Hello,

it well depend on the OS version. From Windows Server 2008 a full format is a new/empty filesystem and an overwrite of all sectors = fully inflated thin disk.

In Windows 2000/2003 a full format is a new/empty filesystem and only a read against all sectors to check for errors. Since there is no writes against the thin disk it is not expanded.

[vmroyale]

Hello.

Good thread - I learned something new today!

This behavior is documented in MS kb 941961.

Good Luck!