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Re: VDDK api VixDiskLib_Create creates 25 MB file size by default

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Hi vigneshrams,

this craete API creates 25 MB file.Is it normal ?

Yes.

Is so does the size of file increase depending upon createParams.capacity ?

 

 

Yes.

Why is so ?

 

 

This is due to the internal layout of hosted sparse disks. As the name indicates the sectors of those disk are not allocated at creation time. But the so called Grain Tables are. Each Grain Table Entry tells whether a contiguous cluster of 128 sectors, i.e. a Grain, is actually allocated in the sparse file. As far as I can remember the Grain Table Entry size is currently 64 bit == 8 byte, i.e. 419430400 / 128 * 8 / 1024 / 1024 = 25 MB.

 

For further details on the inner workings of VMware disks please get a copy of the Virtual Machine Disk Format (VMDK) spec.

--

Thomas G.


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