HBA - "Single Port" vs "Dual Port"

[Deeptanshu Gupta]

We have to connect our DL580 G7 with SAN . I concern is should I procure 2 Single port HBA or 1 Dual port HBA. My understanding was to have 2 Single port HBA as 1 dual port HBA will be single point of failure. I was recommended by my vendor to procure 2 x HP StorageWorks FC1142SR 4Gb PCIe Host Bus Adapter(AE311A). this card has 2 ports but its single channel. I am confused now.

Will there be any configuration limitation to have 2 Single port HBA rather than 1 dual port HBA ? or will 2 single port HBA works the same way a dual port HBA

And why do we have 2 port in HP StorageWorks FC1142SR 4Gb PCIe Host Bus Adapter(AE311A) when its only single channel?

Please help

[SUBHAJIT KHANBARMAN_1]

Dual port HBA and single port HBA has been designed based on the situations or I can say based on the availability of IO slots you can use.

Server like HP DL580 having 6 IO slots so you can use single port HBAs but HP DL380 having 3 IO slots where you need to use dual port HBA so that you can use other IO slots for NIC and all.

Now two single port HBA is always good over one dual-port HBA because of redundancy.

Single port HBA spreads IO acress multiple PCI slots so gives better resilience. Each adapter having it's own PCI bus so throughput is better.(Again depends on PCI technology)

There are several issues at hand here:

1> How many slots you have for HBAs. If you only have 1, go with Dual/Quad Port.
2> How many PCI Busses you have. If you have only 1 buss, go with Single/Dual/Quad Port in multiple slots. Why? If a slot fails you are still up. However if the bus fails you are down. If you have multiple busses, place the HBAs on different busses.

[Deeptanshu Gupta]

And why do we have 2 port in HP StorageWorks FC1142SR 4Gb PCIe Host Bus Adapter(AE311A) when its only single channel?

[SUBHAJIT KHANBARMAN_1]

As per my understanding cost is the main factor here.

For customer who are not much aware of the technology they are going for single channel 2 port HBA because of low cost but who are all aware of technology they will go for dual channel 2 port HBA even though high cost.

For official link please refer below,
http://h18000.www1.hp.com/products/quickspecs/11941_div/11941_div.PDF

http://h18000.www1.hp.com/products/servers/proliantstorage/adapters/singlechannel/benefits.html

[Moderator edit: Removed the broken links. Please refer to https://support.hpe.com/]

[Johan Guldmyr]

One fibre in the fibre cable is for sending and one for receiving. That's why the single port actually has two smaller ports "inside it".

[Deeptanshu Gupta]

thanks for the reply.

my concern is not cost. i just want to understand the difference between 2 port single channel or 2 port dual channel.

i dont want to have this card as a snigle point of faliure. i understand that 2 single port single channel cards are better than 1 dual port dual channel card. but my confusion is dual port single channel card.

i hope you are getting my point

[Johan Guldmyr]

Does it look like this:

http://h18000.www1.hp.com/products/storageworks/images/pciehbaql/170x190-pciehbaql.jpg

Or like this:

http://h10003.www1.hp.com/digmedialib/prodimg/lowres/c02744053.jpg

?

[Deeptanshu Gupta]

this is the link

http://h10010.www1.hp.com/wwpc/in/en/sm/WF06b/12169-304608-336885-336885-336885-1809835-1809834.html

[SUBHAJIT KHANBARMAN_1]

With Single channel single port HBA one WWNN and one WWPN.

With single channel dual port HBA one WWNN and two WWPN.

With dual channel dual port HBA two WWNN and two WWPN.

So in case of zoning these matters.

[Uwe Zessin]

Looks like somebody has put a wrong picture on the page that Deeptanshu Gupta gave the link to.

[Deeptanshu Gupta]

SUBHAJIT

so which one should i prefer - ONE "2 ports" or Two "Single port" ?

[SUBHAJIT KHANBARMAN_1]

I would suggest to go for single channel single port HBA as in your case DL580 G7 means 6 IO slots.

Again check the cost of single channel single port HBA and single channel dual port HBA.

Also, it depends as per your SAN design requirement means how you want to implement the zoning.

Finally, check the factor cost, zoning requirement and decide.

[Deeptanshu Gupta]

if i choose single channel dual port HBA wont that use 2 ports on each SAN switch as-well?


is there any limitation of single channel sngle port card ?

[Uwe Zessin]

> Also, it depends as per your SAN design requirement means how you want to implement the zoning.

Use WWPN-based zoning. It does not matter if you use single- or dual-port adapters.

[Deeptanshu Gupta]

if i choose single channel dual port HBA wont that use 2 ports on each SAN switch as-well?

We do soft zoning i.e. LUN binded to WWNN.

[Uwe Zessin]

No, it won't. one HBA-port goes to one switch-port. Usually, "port" means the same as "channel".

As already explained above: a "port" might look like "two connectors/plugs", but that is because one optical "line" carries the port's receive light while the other carries the light that the port transmits.


Take a look at the picture on Johan's link:
http://h10003.www1.hp.com/digmedialib/prodimg/lowres/c02744053.jpg

That is a single "port". One connect point receives the light from another port while the other ejects light to that port.

[Moderator edit: Removed the broken links. Please refer to https://support.hpe.com/]