ONTAP Hardware

We have stack of 6 DS2246 disk shelf ,planning to add 1 DS4243 disk shelf


Hi Team,


We have Stack of 6 DS2246 disk shelf connected to FAS3210 running 8.2.4 7mode,we are planning to add 1 DS4243 disk shelf.


  1. Willing to know if connecting DS4243 make entire stack to serve at 3gbps,we have data serving on DS2246 so confirming .
  2. Is there way to confirm what is current backend bandwidth utilization on netapp.


From compabiltiy point am sure it works,only worried about perforamce





According to my information, yes, stack speed will be throttled down to the slowest IOM.


just curious to know if there are no additoional SAS ports avaiable on the controller


An easy way to fix the mismatch would be to purchase 2 x IOM6's to swap out with the IOM3's - ONTAP will essentially treat it as a DS4246 (even if the HDD's themselves are 3Gb/s SAS.).


If you don't go that path, it's not really a blanket statement that everything is throttled down to 3Gb/s on the stack.


SAS is a point-to-point protocol. The speed of a connection during its duration will depend on the components in the path of the connection.

If the path goes through a IOM3 in the DS4243 shelf or terminates on a 3Gb/s HDD/drive, then the connection for that I/O transaction will run at 3Gb/s.

If the path to a 6Gb/s drive only has 6Gb/s components in it, then the transaction is at 6Gb/s.


Let's assume that you have multi-path HA cabling (MPHA) and you put the DS4243 at one end of the 7-shelf stack.  

ONTAP will choose the "shortest path" to the HDD/drive.

This will mean that 4 of the shelves will be accessed from one end of the stack while the other 3 will be access from the other end of the stack (again, assuming you have properly cabled for multipath HA (MPHA).


So, this means that 4 of the 7 shelves will be able to form SAS connections at 6G/bs speeds 100% of the time.  The other 3 (including the DS4243) will run with 3Gb/s connections if the path goes through the DS4243 first (at the end of the stack).


Having said all that, I doubt you'll see any tangible performance difference, anyway. Even 3Gb/s SAS is 4 x 3Gb/s lanes = 12Gb/s bandwidth for that path to the 3 shelves from each controller's SAS HBA port.