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I had a chance to work with one of my most talented customers this past week. This came up where we saw different port speeds when looking into an unrelated issue with a Data Domain system:




This is a snippet of what we saw. Focusing on the yellow highlighted ports above, we were seeing different speeds for basically the same physical connections, both 12 Gb and 24 Gb.


Well here’s why – Data Domain offers a couple of different models of shelves. We’ll focus on the ES30 SAS and ES30 shelves for this post. At a very high level, ES30 SAS shelves have SAS drives in the enclosure and ES30 shelves have SATA drives in the enclosure.


An ES30 enclosure will clock back to the head unit or controller of the Data Domain at 12 Gb, yet communicate with other SATA enclosures at 24. However, an ES30 SAS equipped shelf will clock at 24 Gb with the head unit or controller of the Data Domain as well as 24 Gb with other ES30 SAS shelves.


Here’s a quick glance table:

Shelf Type

Speed to Controller

Speed between Shelves


24 Gb

24 Gb


12 Gb

24 Gb


This was with a certain model Data Domain, but from my understanding this should be consistent amongst the different models.