@Marty at ARA I would recommend checking with EMC because they are well known about the performance advantages. 

If you are questionning about emulating LTO5 or LTO8 tapes or drives on your existing DataDomain (which would be able to emulate them), then it’s a question about capacity you need to backup, and virtual tape usage. 

LTO5 capacity is not the same as an LTO8, so their in-line deduplication engine and weekly post deduplication tasks would take more or less time, and free more or less virtual space dependening on the LTO generation you would have selected, but also the amount and type of data that you would have selected.

If you are using Commvault with Datadomain, it mostly means that you disabled Commvault’s deduplication and are relying on DataDomain’s. Then, good luck. I had that kind of setup, I got rid of it quickly.

The question is specifically about performance. Does a VTL LTO-8 drive perform better that LTO-5. I would assume this is something known to Commvault (and Dell for that matter), but no one is able to provide me with a definitive answer.

Well, Commvault is only a client of the physical infrastructure it is installed onto.

Like, if you are able to feed an LTO8 drive with continuous throughput of data, then LTO5 has 3 times less instantaneous performance.

Depending especially on your hardware infrastructure, and also from the data source of your backups, then it’s mostly on the Dell vendor part that you may get more pieces of the answer to your question.

Like, you have a physical MediaAgent with lots of ethernet and FC connections and bandwidth from the infrastructure you need to backup, and let’s also consider you have top performance source infrastructure, then theoretically on LTO8 you would write data faster than on LTO5.

But as you know, it’s only emulated on Datadomain VTL. So it may not matter that much.

IMHO, it’s mostly Dell that would be able to answer, not Commvault.