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Difference between single and dual ports/SAS

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Difference between single and dual ports/SAS

Can anyone help me with a definition of single port and dual port and how important they are when I am looking at SAS drives?

I heard that "SAS is a dual-port interface that provides two separate data paths into the drive." But then, what is SP and DP???
5 REPLIES
Patrick Terlisten
Honored Contributor

Re: Difference between single and dual ports/SAS

Hello,

there are two types of SAS disks: Disks with one port, and disks with two ports. Those with one port are single port, with two ports are dualported. To use DP disks you need a proper enclosure and HBA for it, like an MSA70 and SC44Ge. DP is only supported with HP-UX and OpenVMS. If you're running Linux, Windows, Netware or anything else then HP-UX or OpenVMS, you can buy single port disks.

The second port used for redundandy, so that a disk is still available after a path or controller failure.

Best regards,
Patrick
Best regards,
Patrick

Re: Difference between single and dual ports/SAS

"The second port used for redundandy, so that a disk is still available after a path or controller failure."

Now that's a real bummer! Here I was thinking it had something to do with speed!!!
But if DP is only supported on OpenVMS and HP-UX, why does HP offer both SP and DP drives for the ProLiant servers which support neither of these OSs...

Please do enlighten me.
Is the second port for redundancy alone?
Patrick Terlisten
Honored Contributor
Solution

Re: Difference between single and dual ports/SAS

Hello,

the second port won't be used in a ProLiant, only in MSA60 and MSA70 Enclosures with the right HBAs. There are AFAIK some Integrity servers which also support DP drives.

Take a look at this thread:

http://forums12.itrc.hp.com/service/forums/questionanswer.do?admit=109447627+1206645013954+28353475&threadId=1210934

And the MSA70 QS:

http://h18000.www1.hp.com/products/quickspecs/12652_na/12652_na.html

Best regards,
Patrick
Best regards,
Patrick

Re: Difference between single and dual ports/SAS

Lovely, thank you very much!!!
That explains a lot!
YAQUB_1
Respected Contributor

Re: Difference between single and dual ports/SAS

Hi Prasanna,

SAS is a point-to-point serial architecture that is far simpler than its parallel predecessor SCSI,
yet offers significantly higher throughput (3Gb/sec) as well as better scalability.

Please see the following link:-
http://forums12.itrc.hp.com/service/forums/questionanswer.do?admit=109447627+1206644034961+28353475&threadId=1210934

Hope fully above link full fell your requirements.

Thanks--Yaqub
HP Support!!!