we have a DD690g that we added to our environment 100 days ago. We continue to add more systems to it as we go along, but are currently getting in the area of 22x - 25x rate doing a wide variety of different systems. It takes some patience to keep adding machines slowly until you can determine how much you can safely hold on it, as it is a lot harder to free up space after the fact, than it is to add it! The big thing with the DD, is that you want to set your media multiplexing to 1 for your jobs, as well as make sure that the data you back up doesnt have any sort of compression on it.
our current layout is daily fulls of all systems that write to the DD, and we are doing 30 concurrent jobs to it at a time. We are using a SLP to keep the data on the DD for 30 days, but we also replicate the data daily as well as for the month end jobs we write it out to tape with a 1 year retention. This will cut the dedupe rate down a bit by not keeping it longer than 1 month, but it makes sure our most important (ie recent) data is on disk. We backup 60 or so unix hosts, 10 or so windows hosts, 2 vmware hosts and in that we are sending oracle RMAN data as well as exchange store backups to the DD. I was not a big fan of bringing it in here, but it seems to do a good job. The backup speeds on an individual stream basis seem to be a little slower than going to an lto3/4, but the aggr speed of doing more jobs at a time more than offset that, and the restore times are much better...
