My advice would be to first check the v7.6 and v7.7 HCL from here:
https://support.symantec.com/en_US/article.TECH59978.html
...and look at all of the different features that anythign supports, and try to determine which of those features it is that you need. Before then checking to see which proposed platforms support the the features that you identified as being required.
One tip: Is that not all platforms support "Accel_VMware" i.e. Accelerator for VMware.
You may also want to look for features like Opt_Dup, and AIR.
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Then you'll probably have to get data sheets and tech specs for each platform and look for differentiators.
Questions to ask:
1) Is de-dupe 'in-line' on the fly, or does backup have to be first be stored in a landing-zone before then being processed by de-dupe engine?
2) How often does clean-up occur? i.e. the removal of de-referenced de-duplicated data that is no longer referenced by any backup image?
3) Does the de-dupe platform use its own spare time to tune itse;f up, i.e. re-arrange de-duped data so that related de-duped data is gathered together into a more performant locality to each other i.e. does the platform spend it's idle time preparing to make any restores perform better.
4) Expansion options? How much disk space can be added to a target de-dupe platform? Remember part of the cost of any de-dupe platform has to be in the 'server head unit' that performs the de-dupe - and so, the more disk that you can add to a 'server head unit' before you need to buy another 'server head unit + disk', then the cheaper that platform might be in $/GB.
5) Energry. Some de-dupe platforms are more power hungry than others. Your data centre manager should be able to give you a $ per kWh cost figure. Find out the kWh and work out your 3yr or 5yr energy costs.
6) Rack space U per GB? Ratio of rack space required.
7) Cost of software and hardware maintenance over 'n' years?
