Well to give you some history on this one. Originally with this customer there were 4 servers being backed up to DLT. This took around 10 hours and getting longer (this is pushing the window for most people). So we implemented for them LTO-2 drives in the library(30 tapes including mail slot) I mentioned.
This cut the backup time down to 2 hours (pretty impressive).
SInce then however the number of servers has increased considerably, so has the amount of data (there is now a SAN in place). In addition the backup window is now 3 hours or less (the LTO-2 s are taking around 5 hours to do the job, includes Exchange, SQL etc, etc).
So next on the agenda was a backup to disk directly attached via Fibre Channel to the SAN. This cut it right back down again to the 2 hours to backup with little optimisation. Once completed the backup to tape begins, and runs at its own pace (now takes 3-4 hours to do its job as its directly backing up from the disks which is much faster).
So we end up with 2 backups local and offsite in around 5 hours which is the same as the backup to LTO-2 took before... Total data is about 400-500Gbs (I can't remember exactly). Now we can also implement day time differential or incremental backups too as it won't affect the users whatsoever, and run that off to tape as well, all in the course of a day! Its being considered LTO-3 next just to reduce the quantity of tapes stored, and we can always add another REO box to increase the disk capacity (currently 1.8Tb).
Hope this helps :)
Rob
