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Question

Dell 2950 with SAS - switching to SATA possible?

by May 7, 2011 11:47PM PDT

I have a Dell 2950 with SAS disks installed from Dell. I want to replace the SAS disks with Seagate 1.5TB SATA disks. I've read conflicting info regarding the need for a special "interposer" board which sits between the SATA disks and the SAS backplane:

http://www.lelong.com.my/dell-poweredge-sata-sas-interposer-card-hot-plug-sata-33550488-2009-06-Sale-P.htm

Most posts say it isn't necessary:

http://en.community.dell.com/support-forums/servers/f/906/p/19331920/19695227.aspx

http://www.baasaa.info/20110409/dell-2950-with-perc-controller-can-i-swap-my-sas-drives-for-sata-drives/


But other posts say it is (or might be?) required:

http://en.community.dell.com/support-forums/servers/f/906/t/18463615.aspx#18586627

http://en.community.dell.com/support-forums/servers/f/906/t/18742269.aspx

Does anyone know what the deal is with this interposer board? Does it perhaps add some extra performance that I wouldn't get by plugging the SATA directly into the backplane?

I plugged the 6 SATA disks directly into the system, built a RAID5 in the PERC utility, and had no issues. But I would rather not have everything fail in the near future due to some necessary piece of hardware.

Any help would be great.

Thanks!

Discussion is locked

3 Posts
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Answer
Interposer Boards Rarely Needed
by Jun 21, 2011 3:52AM PDT

The interposer board is only used for specific drive trays. The trays that require the interposer are the trays that have the screws on the side at a distance that doesn't allow the drive to reach the backplane connectors. The interposer does nothing more than "reach" from the drive to the backplane. No other function is provided. It's just an extension cord of sorts. If your drives already reach the backplane connectors in the trays you're using, you don't need the interposer boards. If they don't, you either need interposers for each drive, or get new trays. The trays are a third of the cost of an interposer, so why anyone would ever buy an interposer board is beyond me (unless they are lazy and don't do their homework). Even the trays from a PowerEdge 2850 work great as long as the little blue pegs are removed from the sides (they come out easily if the face is unscrewed from the tray).

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Update
by Dsalas13 Jul 17, 2012 5:21AM PDT

Hi jems 42, I am looking to do the same on a couple 2950's that I have. Just wondering how its going for you. Also how about mixing sata and sas? I want to do a raid of SAS for the OS and raid of SATA for storage. Going to run esxi on it.

thanks

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Answer
"Scampcat's" response is NOT correct
by Feb 6, 2014 4:44AM PST

scampcat said: " Interposer Boards Rarely Needed... The interposer does nothing more than "reach" from the drive to the backplane. No other function is provided."

Per my understanding, you are wrong. The Interposer board actually makes a standard "single-port" SATA (all SATA drives are 'single-port') into a "dual-port SAS" drive. It basically adds the capability to use two data channels. This, in essence, also allows for a bit faster speed/access to/from the SATA drive, as well as adding a redundant data channel. Also, I believe the voltage is slightly different without the Interposer - not sure of the exact specs, since it is shrouded in mystery.

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