What do you recommend when use a SAN with dual controllers and dual fiberswitches.
1. Singel HBA in every ESX3.5 host.
2. Two singel port HBAs in every ESX host.
3. One Dual port HBA in every ESX 3.5 host.
Like mentioned before go for option 2: two single port HBA's
We choose this option too for HBA redundancy.
However if you lack PCI slots you don't have this choice and have to go for the dual port HBA.
Why use dualport HBA at all? If connect to two different SANs?
In the first place some 1U servers don't have extra PCIe ports. In the second place, what's wrong with DUAL port? -NOTHING. Having 2 ports built into a single HBA is exactly the same as 2 HBA, just because it's 2 different SAN makes no difference how you configure the ports. The ports are still separate.
if you lose one path, you have a redundant means of getting to your data.
Having a Single HBA with 2 ports still allows you rudundant paths. The ports aren't married, just combined on 1 HBA, so it's the same as 2 HBA. And if someone wants to argue that it's a single point of failure, ask yourself (or investigate) when was the last time an HBA failed, single, dual port or otherwise, huh? Yeah NEVER. NIC/HBA don't fail. And if your 1 HBA fails and you lose your "second" path, you still have to bring the ESX machine down to replace it.
So 2 Single Port HBA = 1 Dual Port HBA when it's all said and done.
But in a HA situation one dual port HBA is a single point of faulure.
Technically still not true. It's a single CARD, but 2 DIFFERENT chips. EACH chip operates a single port. It's not one chip split in half to run both ports. If a port fails, the other ports still works.
So that eliminates point of failure. Talk to Qlogic or Emulex, they only thing that could happen is if the entire slot that the card is in failed, but if that happens you have bigger problems than HBA.
The card is still 2 separate functioning ports, they are just combined on one card. You think Emulex/Qlogic would actually make an enterprise product that would fail if one port went down? They already thought of that.
Last time an HBA failed for me? October. It happens, especially when you have a lot of them. Meanwhile, you now have TIME to move your vm's to another host. Do you have that if the SLOT just died that has the HBA on it?
Yeah, if it's 1u, and I don't have a choice, then certainly a dual port....The fact is, in order of predictive failure, it will be--human error (config), switch port, fiber, and finally ...the hba. You eliminate 95% of the risk by using a dual port, and even with dual hba's, you still have some risk.....but it greatly improves redundancy.
And yes, I do have dual port hba's in my house, 89 of them....Like I said, when you only have the one option, it's better than the next option, but it's not preferred....