Dual HBA or two Single HBA cards?

[Hardydrewandthenancyboy]

We're setting up a db cluster with two dl380s and an msa1000. We want to do multipathing too.
Is it better to have two separate single HBAs or one dual HBA? If a dual card fails I'll lose both paths so Im guessing two singles is better? Can anyone confirm?

[Amar_Joshi]

Hi Kevin,

You are right to say that dual card is like putting all the eggs in one basket.

Advantage of Dual port FC-HBA card:
1. when you are running short of PCI slots or you are looking at future PCI card installation in server.
2. easy to remember WWN because they are just an increament.
3. one stop BIOS upgrade.
4. $$$ savings

Disadvantages of dual port card:
1. hardware failure may bring down the whole card.
2. individual BIOS upgrade can't be done for testing purpose (though it's highly recommended to test these kinda upgrade on test servers and should be done both at once.)
3. easy to get confused between port A and port B (not joking, seen it several times).

If $$ permits I will go with 2 single port HBAs.

Hope this helps.

[Hardydrewandthenancyboy]

Thanks I'll go with the single hba's then. While I'm at it though; we're implementing secure path on the new db cluster. Does this new switch, controller, hbas etc affect the existing SAN set up for servers that are running at the moment in single path mode? (I'll attach a rough diagram.)

[Stephen Kebbell]

Hi,

yes it could affect it.
The MSA1000 is active/passive. The 2nd controller is standby only. If one of your multipath servers intiates a path failover (e.g. failed HBA or broken cable) then the multipath software will failover to the other path, thus moving all I/O to the other MSA controller. This means your single path servers would lose their disks.

You should probably consider a 2nd HBA for your single path servers, and multipathing software for them.

Regards,
Stephen

[Hardydrewandthenancyboy]

So if everything is running through existing controller A and one of the new servers initiates a fail over to controller B. *All* I/O stops on the controller A so that B can take over? Regardless of zoning etc? If so this is going to change my plans quite a bit.

[Hardydrewandthenancyboy]

closed