Difference between single and dual ports/SAS

[Prasanna Venkatesh]

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???

[Patrick Terlisten]

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

[Prasanna Venkatesh]

"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 · Accepted solution]

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

[The above link is no longer valid]

And the MSA70 QS:

https://h20195.www2.hpe.com/v2/gethtml.aspx?docname=c04140655

Best regards,
Patrick

[Prasanna Venkatesh]

Lovely, thank you very much!!!
That explains a lot!

[YAQUB_1]

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

[The above link is no longer valid]

Hope fully above link full fell your requirements.

Thanks--Yaqub
HP Support!!!

[ajai4evr]

How can differentiate/identify between Dual port and single port via command line? In other words, how can i identify the disk is dual port or not via command line?