AFAIK, DAT and BAK files are same just the difference of extension and they contain data in binary undocumented format.
CAB is a cabinet file, which is a group of files, used by Microsoft to be used as a package for webparts, solutions and templates. It is worth noting that STP , WSP are also CAB files only with just different extensions to indicate context.
They can be crated with makecab.exe
I am still not exactly clear as to when and why I should be using the various file extensions. I think what is confusing is that I have yet to see a piece of backup documentation that mentions them all at once. I suppose that I will just use the .bak extension for my nightly stsadm backup routine. So far I know of the following extensions that work correctly…
Are there any other types?
If I am not wrong wid my thinking , you can use any extension possible. The point is, the backup is just a binary file with stream of bytes. So you cannot use anything as long as you provide exactly same name while restoring.
Remember, extensions just help us in determining the type of file. They do not define the contents.
For ex, if you remane the .xls file to .bmp, it does not become a picture ... Got my point ??
You are correct, however if you change a .bmp file to .xls you will not be able to open it in programs like Photoshop. I figured that this was a similar situation. Regardless, thanks for the tip Madhur.
Also, Mike Walsh added this bit of information as well...
"It doesn't matter which extension you use for your stsadm backup. Todd
Klindt in chapter three of the Real World SharePoint 2007 book (the
chapter on SP administration) where he gives a lot of info on using
stsadm in real life, suggests using a completely different extension
(such as .stsadm - not sure if that exactly was what he says, but
similar) so that you can immediately identify them as stsadm backups and
nothing else that is using the rather common .bak file name.
Seemed a good idea to me when I read it."