How many VMs on a Single HBA?

[Heartstealer]

Hi All,

I am designing a VI3 environment for a client, however I am doubtful if HBAs will be a bottle neck for VM performance. I would like to know how many minimum I should recommend? Will two suffice one primary and another for failover? can we do load balancing for HBAs? I have read that we can have many number of VMs communicating through a single HBA however, will there be any performance issues? Can anybody share their experiences and recommendations?

Thanks

Rahul

[Karunakar]

Hi Rahul,

I think there should not be any problem to have multiple VMs over a single HBA.

I have 10 luns shared on to my machines with 8 to 10 VMs, and no issues on performance.

I'm not sure with the load balancing stuff over HBA, but make sure you have multi pathing enabled for the luns presented to that HBA.

-Karunakar

[LarsLiljeroth]

Hi

In general i don't see that you would have a bottle neck on your HBA. In most cases it's the CPU, Mem, Nic i/o.

But again it depends on the storage traffic.

So i would always go for 2 Hba per. host . This will give your redundancy and also, if your storage systems is active/active you will be able

to do loadbalancing.

My expirience is that we only utilize our HBA about 10-30 % in the most active esx host. That is hosting about 30 servers.



Best regards

Lars Liljeroth

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[Heartstealer]

Hi Lars / Karunakar,

Thanks for you comments and time you took for answering this. I think I understand what Karunakar is saying ...

However, lars are you saying that its ideal to have two HBA cards or 2 port * 2 HBA cards (total 4 ports) ? I also need to give RDMs to some of these VMs on that ESX with just 2 HBA ports will that affect anything?

Thanks and regards,

Rahul

[RobBuxton · Accepted solution]

I've not seen HBAs as a bottleneck, even more so with the 4GB HBAs now commonly available.

In our Blade Servers I have single dual port HBAs and in the 1 U Servers I have run 2 x single port HBAs.

The main SAN issues I've had have been a dodgy tranceiver and a fault motherboard on a Blade Server.

Otehrwise the HBAs themselves have been pretty sound which is why I'm not too concerned about going to single dual port HBAs on the Blade.

A lot of the design is about redundancy and how much risk / single points of failure you're prepared to tolerate.

[williambishop]

I'd have to agree with the others. I've never seen HBA's being a bottleneck, even if all of the guests goes through a single one. And with nearly a hundred hosts, and thousands of guests, I'm sure I would have seen it if it were a likely issue.