Tag Archive for VMDK

Creating new VMDKs – What Mode should you use?

October 18, 2012 Storage, VMware No comments

There are 3 Disk Modes within the hard disk options.

  • Independent – Persistent

Disks in persistent mode behave like conventional disks on your physical computer. All data written to a disk in persistent mode are written permanently to the disk. You can set a virtual disk to independent mode to exclude the disk from any snapshots taken of its virtual machine. Changes are immediately and permanently written to the disk, so they have high performance

  • Independent – Non-Persistent

Changes to disks in non-persistent mode are discarded when you power off or reset the virtual machine. With non-persistent mode, you can restart the virtual machine with a virtual disk in the same state every time. Changes to the disk are written to and read from a redo log file that is deleted when you power off or reset. You can set a virtual disk to independent mode to exclude the disk from any snapshots taken of its virtual machine.

  • Normal

In normal mode, disks are included in snapshots that you take of the virtual machine. If you do not want data on the disk to be recorded when you take a snapshot of the virtual machine, configure the disk to be independent.

How to shrink VMware VMDKs

October 18, 2012 Storage, VMware No comments

Shrinking a Virtual Disk

Shrinking a virtual disk reclaims unused space in the virtual disk and reduces the amount of space the virtual disk occupies on the host.
Shrinking a disk is a two-step process. In the preparation step, VMware Tools reclaims all unused portions of disk partitions (such as deleted files) and prepares them for shrinking. This step takes place in the guest operating system.
In the shrink step, the VMware application reduces the size of the disk based on the disk space reclaimed during the preparation step. If the disk has empty space, this process reduces the amount of space the virtual disk occupies on the host drive. The shrink step takes place outside the virtual machine.

When can you not shrink a disk?

Shrinking disks is not allowed under the following circumstances:

  • The virtual machine is hosted on an ESX/ESXi server. ESX/ESXi Server can shrink the size of a virtual disk only when a virtual machine is exported. The space occupied by the virtual disk on the ESX/ESXi server, however, does not change.
  • You pre-allocated all the disk space to the virtual disk when you created it. Must be Thick provisioned drive for Shrinking
  • The virtual machine contains a snapshot.
  • The virtual machine is a linked clone or the parent of a linked clone.
  • The virtual disk is an independent disk in non-persistent mode.
  • The file system is a journaling file system, such as an ext4, xfs, or jfs file system.

Prerequisites

■  On Linux, Solaris, and FreeBSD guests, run VMware Tools as the root user to shrink virtual disks. If you shrink the virtual disk as a nonroot user, you cannot prepare to shrink the parts of the virtual disk that require root-level permissions.

■  On Windows guests, you must be logged in as a user with Administrator privileges to shrink virtual disks.

■  Verify that the host has free disk space equal to the size of the virtual disk you plan to shrink.

■  Verify that all your hard disks are thick or this will produce an error when you click Shrink

Procedure

  • Click the Shrink tab in the VMware Tools control panel.

 

  • If the disk cannot be shrunk, the tab shows a description of the reason.

  • Select the partitions to shrink and click Prepare to Shrink.

If you deselect some partitions, the whole disk still shrinks. The deselected partitions, however, are not wiped for shrinking, and the shrink process does not reduce the size of the virtual disk as much as it would with all partitions selected.
VMware Tools reclaims all unused portions of disk partitions (such as deleted files) and prepares them for shrinking. During this phase, you can still interact with the virtual machine

  • When a prompt to shrink disks appears, click Yes.

The virtual machine freezes while VMware Tools shrinks the disks. The shrinking process takes considerable time, depending on the size of the disk.

  • When a message box appears that confirms the process is complete, click OK

The Newer Compact Command

Some newer versions of VMware products include a Compact button or menu command, which performs the same function as the Shrink command. You can use the Compact command when the virtual machine is powered off. The shrinking process is much quicker when you use the Compact command.

Method 1 – Using VMware Converter to shrink or extend a disk

  • Install VMware Converter on the machine you want to convert
  • Start the VMware Converter Application
  • Select File > New > Convert Machine > Select Powered on Machine
  • Specify the Powered On Machine as Local Machine
  • Note, you can also select File > New > Convert Machine > VMware Infrastructure Virtual Machine if you want to shrink a VM which is powered off but you will need VMware Converter installed on another machine

  • Click Next

  • In Destination Type, select VMware Infrastructure Virtual Machine
  • Put in vCenter Server Name
  • Put in User Account
  • Put in Password
  • Click Next

  • Type a different name for your VM. You cannot use the same name
  • Select the same Resource Pool you use for the machine you want to convert
  • Click Next

  • Choose a destination Resource Pool or host
  • Click Next

  • Click Edit on Data to Copy

  • Select Advanced

  • Select Destination Layout
  • Select the disk you want to change the size of by clicking the drop down button and select Change Size

  • Click Next
  • You will reach the Summary Page
  • Click Finish and the following window will open and show you the running task

  • Power off the original VM
  • Power up the new cloned VM and check everything works ok
  • Delete the original VM

Best Practices for using VMware Converter

http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1004588

VMware VMDK Files

June 27, 2012 Storage, VMware No comments

VMDK Files

These are the disk files that are created for each virtual hard drive in your VM. There are 3 different types of files that use the vmdk extension, they are:

  • *–flat.vmdk file – This is the actual raw disk file that is created for each virtual hard drive. Almost all of a .vmdk file’s content is the virtual machine’s data, with a small portion allotted to virtual machine overhead. This file will be roughly the same size as your virtual hard drive.
  • *.vmdk file – This isn’t the file containing the raw data anymore. Instead it is the disk descriptor file which describes the size and geometry of the virtual disk file. This file is in text format and contains the name of the –flat.vmdk file for which it is associated with and also the hard drive adapter type, drive sectors, heads and cylinders, etc. One of these files will exist for each virtual hard drive that is assigned to your virtual machine. You can tell which –flat.vmdk file it is associated with by opening the file and looking at the Extent Description field.
  • *–delta.vmdk file – This is the differential file created when you take a snapshot of a VM (also known as REDO log). When you snapshot a VM it stops writing to the base vmdk and starts writing changes to the snapshot delta file. The snapshot delta will initially be small and then start growing as changes are made to the base vmdk file, The delta file is a bitmap of the changes to the base vmdk thus is can never grow larger than the base vmdk. A delta file will be created for each snapshot that you create for a VM. These files are automatically deleted when the snapshot is deleted or reverted in snapshot manage