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Backing up virtual machines on VMware ESX Server

I know VMware and Virtual Server technology is becoming more and more prevalent in organizations as both packages can greatly reduce hardware costs. We've been testing VMware ESX Server heavily because of its ability to overallocate memory, its very small footprint as a host operating system, and the ability to use VMotion. Virtual machines also tend to be quite nice from a recovery perspective. If you have a copy of the virtual machine file(s), rolling back changes, or bringing up the VM in a disaster situation means installing the host OS/application server, copying in the VMs, registering them, and starting them. Piece of cake!

However, there is an issue with VMware ESX Server if you copy the files from a non VMFS file system. VMFS is VMware's proprietary file system where disk images get stored. Going from VMFS to VMFS there aren't any issues. That's why cloning works so well. However, if you copy from VMFS to another system, such as a Windows system where the files will be backed up, there is an issue. It's covered in the following article:

How should I back up virtual machines used in ESX Server?

Even with the following comment in this article, we've seen some corruption issues which disk files > 2 GB during the transfer:

Some file utility programs can also have problems with files larger than 2GB. SCP and FTP, however, are capable of handling files larger than 2GB. These tools can safely be used to move ESX Server virtual disks to other VMFS volumes, or to back them up on file systems capable of handling files over 2GB. However, be sure to use binary mode when transferring virtual disks with FTP.

We've repeated a copy on and were able to get a successful restore after a failure. This inconsistency is not acceptable. At this point we're likely going to look at a 3rd party backup utility. While we could go down the vmkfstools route, that would mean increasing the complexity, which can lead to problems in a DR situation where minutes are critical. There may also be something simple we're doing wrong, I won't discount that. However, it certainly isn't as easy as it was with VMware GSX Server.

K. Brian Kelley - Databases, Infrastructure, and Security

IT Security, MySQL, Perl, SQL Server, and Windows technologies.


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