VMware GSX Server 2.5.2

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Adding Plain Disks to a Virtual Machine

Plain disks are a type of virtual disk that provides faster virtual machine performance. Since you allocate all the disk space when you create the plain disk, the plain disk runs faster in a virtual machine than a virtual disk. Also, the time it takes to install the guest operating system is reduced. The drawback is that you need to have all the space you want to allocate to the plain disk available when you create the disk. Also, plain disks take longer to create; the larger the disk, the longer it takes to create.

Another area in which they have a place is SCSI reservation (and high-availability configurations). VMware supports SCSI reservation when used with plain disks; support for SCSI reservation with virtual and raw disks is considered experimental. For more information about SCSI reservation, see High-Availability Configurations with GSX Server.

Any plain disks you created in GSX Server 1 can run in virtual machines created under GSX Server 2 and can be shared through SCSI reservation.

To create a plain disk, follow the steps below for your host operating system. You need to specify the size of the plain disk, up to 128GB. Remember that, unlike virtual disks, which grow as data is added to them, all the space the plain disk is to occupy on the host is allocated when the disk is created.

A plain disk is composed of at least 2 files, a .pln file and one or more .dat files. The .pln file is a text file that maps the .dat files to the corresponding sectors of the plain disk. The .dat file or files contain the data for the disk. Each .dat file is limited to 2GB in size. If the plain disk (named, for example, plaindisk.pln) is larger than 2GB, then its .dat files are divided into sets of 2GB data files named plaindisk1.dat, plaindisk2.dat, plaindisk3.dat and so on.

Windows Host

To create a plain disk on a Windows host, you use the Add New Hardware Wizard in the Configuration Editor. When you are creating the new virtual disk, you must make one specific selection. Follow the steps below.

Connect to the virtual machine with a console then choose Settings > Configuration Editor to open the Configuration Editor. Do not power on the virtual machine.
Click Add to begin adding a plain disk. The Add Hardware Wizard opens.
Choose a Hardware Type of Hard Disk then click Next.
Select Create a new virtual disk and click Next.
Specify the size of the disk, check Allocate all disk space now then click Next.
If you prefer, change the name of the plain disk.
If you want to set the disk to run on a specific node, click Advanced.
Specify the node, then click Finish.
Power on the virtual machine and format the plain disk.

Linux Host

To create a plain disk on a Linux host, use the Configuration Editor (Settings > Configuration Editor). The virtual machine should be powered off before you begin. If it is not, shut down the guest operating system normally, then click Power Off on the GSX Server console toolbar.

Connect to the virtual machine with a console then choose Settings > Configuration Editor to open the Configuration Editor. Do not power on the virtual machine.
To add a SCSI plain disk, click the + sign beside SCSI Devices. Click a device on a SCSI controller that is shown as Not Installed.
Select the device type of Plain Disk.
Keep the default mode of Persistent or use the drop-down list to change the setting to Undoable or Nonpersistent.
Type the name for the plain disk's first file. By default, it is created in the same directory as the virtual machine's configuration file. To create it in a different directory, type the full path name or click Choose... to navigate to the directory you want to use.
Set the capacity for the new plain disk. The capacity cannot be greater than 128,000MB (128GB).
Note: Unlike a virtual disk, which starts small and grows as data is added to it, when the plain disk is created, all the space is allocated to it up front. Be sure you have enough room on the host to hold the plain disk you are creating.
If you are connecting to a virtual machine on a Linux host and you want to disable write caching on this disk, click the check box beside Disable Write Caching.
When write caching is enabled, there is a delay between the time a program saves data and the time that data is actually written to disk. This improves performance. But the delay in writing data to disk adds some risk of data loss. Thus if data integrity is more important than performance, you may want to disable write caching.
Click Create to create the files for your new plain disk.
Click OK to save your settings and close the Configuration Editor.
The new plain disk appears to your guest operating system as a new, blank hard disk. Use the guest operating system's tools to partition and format the new drive for use. If you are sharing this disk for clustering, install and set up clustering software on the plain disk.

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