Optimizing VMs for Alike backups

Since Alike globally de-duplicates your virtual machine images, there are several tricks that can yield significant benefits in reducing your overall backup size and job window. A few of these tricks are listed below.

1. Defragment the guest's hard drives on a routine basis.
You can use the defragmentation tool built into your Operating System. Alternatively, for Windows guests, an excellent defragmentation tool for windows is myDefrag, aka jkdefrag. It now supports scripting, and can easily be scheduled to run weekly, or whenever, to keep your virtual disks in shape.

2. Wipe deleted data from your drives.
In most filesystems, when you delete a file, the actual data underneath it is not removed. The space is freed up for you to reuse when needed, but that data is partly still on the disk. Because Alike cannot tell the difference between this partially deleted data and your actual, important data, it will back it all up.
In Windows, Microsoft provides a utility called Sdelete to empty deleted space. Simply use the syntax: sdelete.exe -z, per virtual disk. (Please note, previous versions used the "-c" option instead of the "-z". Please consult the sdelete help file for exact usage)

In Linux/Unix this has a similar effect:
dd if=/dev/zero of=/allZeros bs=20971520 # bs=20m
rm /allZeros

3. Place the system's swap file on a completely separate virtual disk.
Because swap files can grow to be very large, and their contents are constantly churning, they can wreak havoc on a system's deduplication and compression performance. Because Alike analyzes each virtual disk independently, placing the swap files on their own disk will quarantine their activity, and provide a much better deduplication experience for your system/data drives.

4. Disable Anti-virus or Anti-spyware in Alike directories.

These security products can cause serious performance problems with Alike jobs as they constantly intercept Alike I/O calls to the filesystem. They also have the potential to cause job failures if they quarantine data. It is strongly recommended that you exclude the following Alike directories from scanning: DBs, the Data Storage path and the temporary work directory.

5. Make sure you have the proper XenTools installed on your VMs.
The XenTools installation will ensure that your VMs are performing optimally in their virtual environment. Additionally, if you wish to leverage your VSS providers for applications like MS SQLServer or Exchange, you will need to install the XenTool VSS Provider, instructions outlined here.

You can view this article online at:
http://www.quorumsoft.com/kb/index.php/article/optimizing-vms-for-alike-backups