I have spent the last few days trying to find a free backup solution to the newly free ESXi for windows only enviroments (in particular Windows XP). The solution for me was the following:
1. Installing Windows Services for UNIX (WSFU)
2. Copying the ESXi Server password and group files to Windows
3. Configuring WSFU for accepting ESX Server connections
4. Sharing the Windows folder for NFS compatibility
5. Configuring the ESXi Server to mount the Window NFS Share as Datastore.
6. Setup Backup Script
Attached is the complete steps.
I take NO credit for any of this. This is just a complation of others work formated to suit my needs and felt others could benift from it as I have.
The least expensive would be to use the Windows Server backup app that comes with Windows Server. It is basic but does work and can be scheduled. You can use that within the virtual servers as well.
I don't think you should expect to find many free solutions that can handle everything.
Trilead is a good tool but only does VM backups (VMWare ESX/VSphere and Hyper-V)
There is another tool, called Uranium Backup (http://www.uraniumbackup.com) is kind of an alternative to Back Exec.
The Gold Edition, which is about 300€, does all kinds of backups (Standard Windows Backup, SQL, Exchange, ESX, Hyper-V,....)
One license covers backsups of an unlimited number of servers or VM's so in terms of "Bang for your Bucks", it's certainly worth investigating.
We use Appassure Replay (http://www.appassure.com/ - part of DELL) which works with a Replay Core server that does Scheduled Snap-shotting backups (Full + incr/diff) of a number of servers and stores them in a local repository.
There is a built-in retension plan that remove backups, older than a certain age.
The restore function does "point-in-time" restore like MS-SQL.. really easy.
It can replicate the backup data to a remote site where another Replay Core server can create virtual standby systems on ESX, Hyper-V,...
If the main site goes down, you just boot up the virtual standby systems and "presto", you're back in business.
The virtual standby systems can of course also be created locally in case you have a local single server failure.
It does need a dedicated machine that functions as Core Server; Preferably a Quad-Core with 16GB and loads of disk space, 2TB or so depending on how many servers you want to protect and how long your retension periode is.... I love it.
Hope this helps.