ID #1035

How to calculate the disk-geometry

There are several reasons why you want to calculate the disk-geometry manually:

  • change the adapter-type of an existing vmdk
  • create a vmdk description for a dd-file
  • create a vmdk description for a img-file like used by Starwind
  • create a vmdk description for a *-flat.vmdk when the original description is lost

For all cases we first need the nominal size of the disk in sectors.
Look up the size of the image-file in bytes.

<size of image in bytes> / 512 = <size in sectors>

Next decide which type of geometry you want : IDE or SCSI


SCSI

For SCSI-disks the typical geometry is * cylinders x 255 heads x 63 sectors

ddb.geometry.cylinders = *
ddb.geometry.heads = "255"
ddb.geometry.sectors = "63"

To get the number of cylinders calculate
<size in sectors> / 16065 = <number of cylinders>
When the vmdk uses adapertype buslogic or lsilogic this formula is valid for all disks larger than 1 Gb


IDE

For IDE-disks the typical geometry is * cylinders x 16 heads x 63 sectors

ddb.geometry.cylinders = *
ddb.geometry.heads = "16"
ddb.geometry.sectors = "63"

To get the number of cylinders calculate
<size in sectors> / 1008 = <number of cylinders>


IDE larger 8 GB

When the vmdk uses adapertype ide the maximum value for <number of cylinders> is 16383.
So for all disks larger than that - 8Gb - you can use this geometry

ddb.geometry.cylinders = "16383"
ddb.geometry.heads = "16"
ddb.geometry.sectors = "63"

Tags: calculate, disk-geometry, vmdk

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