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I'm using XenServer 5.6 as bare-metal hypervisor and CentOS 5.3 as guest OS. Because of our custom CentOS edition partitioning features, volume size required to install it fluctuate in range from 60 GB to 140 GB. As result XenServer VHD has the same enormous size. Recently there was an urgent need to start working with Templates and Appliances of XenServer, but taking into account the huge size of created images it looks almost impossible to copy/move such file.

Do you have any suggestions how to reduce created file size or compress it? May be there are some third party tools (backup/compressing tools) to overcome this problem?

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I'm not sure of compressing in XenCenter, But even if you shrink it from 60GB to 40GB, your still going to have huge images moving around, and wasting space on your SAN or Hard drive unless you use the advanced disk features of your VM solution.

XenCenter should allow using VHD differencing disks. You would create one Base image file, with a base CentOS image. Then create linked Differencing disks for each VM.

This blog talks about how it is good for the template model:

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To compress your disk you can do this:

  1. shutdown the VM
  2. right click on the vm and say "Export to file...."
  3. after the file is saved to your windows computer, add it to a .rar file with maximum compression
  4. email or send the .RAR wherever it needs to go

If you want to keep the VM's always compressed (at the cost of CPU power), you should consider mounting root, or a part of the vm as JFFS2. This is a compressing filesystem which can be mounted in read-write mode. (most compressing filesystems are readonly). Read more here or here.

You could also create a "fileserver" vm with a very large drive. Share out this drive over NFS and then add it to XenServer as a SR. If you store your VM's on this SR, they will be smaller on disk. I'm not sure if this helps you when moving VM's around, but it's a thought!

I hope this helps! Let me know if you have any more questions.

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