Multipathing / Dual Port / Wide port ?


I am using windows server 2016 as a home pc, so no server .

I have a Lsi Megaraid card with a dual port SAS cable connected to a dual port hard drive.

I am trying to get both ports to show in device manager but I can not seem to figure out how.

I have enabled mpio and checked the mpio properties boxes iSCSI + SAS Support.

That still does not present the dual ports to device manager .

I believe iSCSI initilizor is for IP NIC multipathing , which is no good for me because my SAS multipath disks are connected internally to a PCIe megaraid card.

What do I do to get windows to recognise the dual ports ?

Robert StevensAsked:
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David Johnson, CD, MVPOwnerCommented:
the 2nd port is for redundancy i.e. controller failure (you plug the drive into another controller) the drive will only show up once.

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Robert StevensAuthor Commented:
Hi David

I have heard that connecting it to another controller for redundancy is one option although I believe it’s possible to connect both dual ports of one hdd  also for performance to the same controller. Single controller multipathing.

I purchased 2 x Dual Port cables SFF-8643 to SFF-8680 , I can use 2 of these cables on the 9361-8i allowing 4 x dual port ST4000NM0074 hard drives to be connected to the same 9361-8i megaraid controller ( total of 8 SAS Ports )

The problem i am stuck at is do I use iSCSI initiator because I have tried using the megaraid storage manager IP which is although it fails to connect I think because of the port number 3260 , maybe I need to add a port forward or the MSM login is a issue or is there another option to somehow add a iSCSI target to my MSM storage ?

I am totally new at this and believe it would be real easy using a NIc but I know this is possible and just need some things to try even if they fail any suggestions on what I could do as there is such limited info on this.

Cliff GaliherCommented:
There is no benefit or purpose in trying to do what you are trying to do. And it can't be done in the way you think it can. David Johnsons answer was correct. As for added performance using two cables...nope.  The OLDEST SAS standard could handle 3Gb/s. And chances are your SAS card does 6 or 12. No single drive can write that fast. Mechanical drives top out at 40MB/s. Only the newest fastest SSDs tend to top out at around 400MB/s" and to see that, you'd need a newer SAS card anyways. So one port would never be saturated enough to need a second cable/port to the same card no matter how you slice it.
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Gerald ConnollyCommented:
I am with Dave and Cliff in that it doesnt work like that! The disk can only work on one path, the second is for redundancy.

I do disagree with Cliff's assertion that a mechanical drive can only do 40MB/s however. Maybe 10 years ago Cliff!
Spinning rust drives including consumer level drives can do 70-100MB/s sustained transfers, Enterprise level 15K rpm drives can do 150+MB/s

Modern consumer SSD's tend to top out at around 500-550MB/s mainly limited by SAS bus speeds (6Gbit/sec = 600MBytes/sec).
Enterprise SSD's are 10x or more faster (better connectivity)
Cliff GaliherCommented:
Take your average spinning drive and run it enough to flush the cache (not hybrid)!, they drop to 40/50. Mind you, I am talking AVERAGE here. Sustained near perfect linear reads in high density platters (aka 4TB drives) are not average conditions nor average drives. Which is why storage performance is more often discussed in Oops, not raw throughout.

Put an normal SSD on a 12Gb SAS pipe and it still tops out at 550MB. The bottleneck isn't SAS on a single disk, full stop. I stand by my numbers.
Gerald ConnollyCommented:
Consumer level SSD's normally only have a 6Gb/s Interface
Robert StevensAuthor Commented:
Hi thanks for the responses

The megaraid storage manager handles the dual port, the MSM Backend shows both ports connected and provides SAS addresses. The computer on sees one drive as mentioned by a expert here.

There is two personality options  via CTRL-R LSI Properties during legacy boot
1) Raid

The JBOD personality allows a parameters option to become enabled and inside that parameters is the option to check a box called multipathing. You can still setup raid virtual disk array using the JBOD personality so it’s great news.

Thanks for all the support and I won’t get involved in spinning disk drive transfer speeds , I will say though with these megaraid cards they are faster than what been mentioned here.

Thanks again hope to come back soon
David Johnson, CD, MVPOwnerCommented:
Answer provided was correct
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Windows Server 2016

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