HOWTO: using a raw disk in VMware Server 2.0

I needed to use a raw physical disk from within a VMware image.  This works in VMware Workstation and apparantly also in Server 1.x but somehow the ability to use physical disks was removed from the UI of Server 2.0. While I could find some posts about this on the forum none of them really helped me any further.  After a lot of fiddling and comparing with VMware Workstation I finally found how to make it work.  I hope this is usefull for somebody. If it isn't, just ignore me 

I used the following setup:

My server has 2 'disks': /dev/sda is a local raid used for storing the server os and guest images, /dev/sdb is a chunck of a SAN connected via fiberchannel which will be used by one particular guest called 'barbar'.

• Make sure the guest is powered off before making any changes

• The configuration of the VMware guest image is stored in the <guestname>.vmx file in the guests directory.  The virtual disk configuration consists of a few lines which read like this:

-

scsi0:1.present = "TRUE"

scsi0:1.fileName = "barbar-0.vmdk"

scsi0:1.deviceType = "rawDisk"

-

Note the '0:1' denotes the second disk on the first SCSI channel. This is because I'm using 2 disks in the guest: the virtual disk which will hold the OS and the physical disk which will show up as the second disk. 

• The vmx file does not contains any references to the actual physical disk I want to use (/dev/sdb). This information is stored in a second file (in this case barbar-0.vmdk)  This file looks like:

-

1. Disk DescriptorFile

version=1

CID=e6704746

parentCID=ffffffff

createType="fullDevice"

1. Extent description

RW 419430400 FLAT "/dev/sdb" 0

1. The Disk Data Base

#DDB

ddb.toolsVersion = "0"

ddb.encoding = "UTF-8"

ddb.adapterType = "lsilogic"

ddb.geometry.biosSectors = "63"

ddb.geometry.biosHeads = "255"

ddb.geometry.biosCylinders = "26108"

ddb.geometry.sectors = "63"

ddb.geometry.heads = "255"

ddb.geometry.cylinders = "26108"

ddb.virtualHWVersion = "6"

-

Disk DescriptorFile  I have no idea what the first set of options do. I copied these from a Workstation 6.0.4 setup.

Extent description this line defines which physical device will be used.  In this case I'm using my secondary disk which is /dev/sdb.  The number is very importan, this is the size of the disk in 512b blocks. You can find this by doing 'fdisk /dev/sdb' on the server

-

fdisk /dev/sdb

Command (m for help): p

Disk /dev/sdb: 214.7 GB, 214748364800 bytes

255 heads, 63 sectors/track, 26108 cylinders

Units = cylinders of 16065 * 512 = 8225280 bytes

   Device Boot      Start         End      Blocks   Id  System

/dev/sdb1               1       26108   209712478+  fd  Linux raid autodetect

-

214748364800 / 512 = 419430400

ddb.geometry*  make sure these also match the  geometry of the physical disk. Again you can get this from 'fdisk /dev/sdb' on the server.

The ddb.geometry* info seems to be less important, however the size in the Extent description should be correct otherwise the image won't start.

• now start the guest from the console.  The physical disk will not show up in the guest summary screen, however when you now run 'fdisk /dev/sdb' from within the guest you should see the partition table of the real physical disk

I hope this is useful to somebody

Nico