Load balancing with EVA 3000

[Victor_101]

Hi ,
I have my EVA 3000 setup as shown in the diagram. It came prinstalled. My question is, from the image, only 1 path (PN) is active from each switch to each conroller which basically covers the load balancing IS THE OTHER PATH ONLY STANDBY ? coz i can see activity only on the 1 of two paths..is this normal ? can it be configured to load balance across PN and PN+1 on both switches?

[Uwe Zessin · Accepted solution]

No, sorry, you cannot. On the EVA3000/5000 (like many other storage arrays, by the way) one controller is responsible for I/O management of a single virtual disk at a time.

The other controller presents the disk, too, so that the failover software "knows" that there are standby paths it can switch over in case of a failure, but you cannot route any I/O through these paths.

You can still make use of both controllers by assigning preference of half of the virtual disks to one controller and the other half to the second controller.

[Mark Poeschl_2]

You should be seeing a total of four paths to each Vdisk - two active and two standby. As Uwe says each Vdisk is only active on one controller or the other, but you still have two paths - one out of each HBA - to the Vdisk. The EVA controllers automatically do load sharing across their two ports.

[Uwe Zessin]

Hm, I'd say that it depends on the multipath software and it's setting whether you see two active paths. My experience with Secure Path is that load balancing is turned off by default.

Not that I want to dig too deep into nit-picking, but it is the host which needs to do the load balancing/sharing - a controller is just responding to I/O requests to a specific port. The EVA storage array does kind of load sharing by balancing all virtual disks with no path preference between controllers, though.

[Vincent Fleming]

Mark is correct - there are 2 ports per controller. If your zoning allows, you will see 2 ports per HBA - all ports have the LUNs on them. So, 4 paths.

Uwe is also correct in that each LUN is "owned" by a controller, so you can only do I/O to a LUN via one controller out of the pair - the other controller is standby for that LUN.

Dynamic Load Balancing across the controllers is not supported at this time. You can load balance across ports on a controller, but not between controllers.

Cheers,

Vince

[Uwe Zessin]

Not "supported" ?

:-) That's a good one...

It does not work at all!

Any idea if/when the XCS AAA code will make it into VCS?

[Vincent Fleming]

Uwe, if you're referring to the active/active controller feature, that would be version 4 of the VCS, currently due out end-of-year.

Don't hold me to that, of course...

[Uwe Zessin]

Yes, that's what I meant - thanks, Vince.

I've been on a tour through the qualification labs in CXO a few month ago, so I understand that it will take a bit of time ;-)
Have never seen sooo many fiber cables and literally piles of disk drives.