Hi Andreas!
We have used a product which uses both checksum testing and blocklevel
saving. This product is called ESM (Enterprise Storage Manager). When we
bought it, it was sold by Legent, it's now a CA product.
We found several downsides to both checksum testing and blocklevel
saving.
When you perform blocklevel testing you will have to perform a checksum
routine for every file (or at least for every file larger than xx Kb.).
This causes a lot of overhead. We saw a significant performance impact
on the slower clients!
Checksum testing looks like a nice feature. Why sending and storing one
file on the server more then once? Ok, when client1 stores WINWORD.EXE
and client2 just stores a pointer to the WINWORD.EXE on client1's tape,
you will need a extra tape mount when restoring C:\MSOFFICE on client2.
The restore time will definitely be slower in this case!
So believe me, you don't want to use both features. I can tell from
experience.
Kindest regards,
Eric van Loon