Morning,

I intend to use Powerconnect 6224's for the SAN traffic in my implementation. I am going to bond two NIC's together on Xenserver to create the bonded SAN network. Cables are then going to plug into two seperate (stacked) 6224 switches. Do I need to configure LAG on the switch for these ports? Or is the XenServer bond active/standby?

Thanks

Tim

Hi Tim,
Is this SAN support multipath? If yes than you could go ahead and enable multipath from Xenserver as well.

Regards,
Subash

Subash,

It's a Dell EqualLogic, of which it's dual controllers are active/standby - So I'm guessing its not multipath unless anyone else can throw in their two cents?

Try this article:-

http://support.citrix.com/article/CTX124421

Tim,

This is what I have found out when I configured our EqualLogic PS4000X.

1. Dell TechCenter has documentation on how to configure your EqualLogic with two switches.
a. You should have one NIC in each controller going to different switches. For example NIC 1 on controller a and b go to switch 1 and NIC 2 on controller a and b go to switch 2.
b. Between each switch configure two ports in a LAG group which will be your crossovers between switch 1 and 2. Dell recommends the use of LAG groups here.

2. From my understanding that you should not use a BOND for a storage network because the ISCSI traffic will only be placed on one NIC at a time. While this give you redundancy you lose aggregate throughput.
a. Check out Citrix's Master Class on Networking they gives you a good explanation as to why and how you should use them.

I do have them in a Bond with no problems right now, but I am unable to take full advantage of multipathing since they are in a Bond. Since my environment is not very large I have not had any problems with them in a bond I just do not know if I would have set them up in a bond knowing what I know now from listening to some of the Master Class information.

Anyone at Citrix have a say in how we should be doing this since I have heard it is okay to use a bond for storage and in the same breath that you should not use a bond?

Thanks guys and good luck!

Edited by: RYAN STEVENS on Feb 12, 2011 9:18 AM

The question of whether to use a bond or multipath for a software iSCSI connection is simple.

If you use a standard XenServer bond, traffic will be balanced using SLB , this means that dom0, through which your open-iscsi traffic is flowing, will only be balanced on one NIC in the bond at any one time. This gives you resilience, but not additional throughput.

If you use multipathing, then you can take advantage of both additional throughput and resilience, as the iSCSI traffic will flow through multiple NIC's.

If you use unsupported bonding techniques, discussed in the arctive I referenced, then you can configure active/active bonding, but it must be stressed that this is **unsupported**.

So, the answer is that the first two of the above options are acceptable, but your choice will depend on what functionality or performance you need from the solution. If bonding is working for you and the performance is acceptable, then I would stick with it, multipathing introduces more moving parts, but if you have the inhouse expertise to implement and manage a multipath environment, go for it.

Guys -

Something I just read from Citrix which is important to this discussion is:

In version 5 of XenServer Multipathing was not supported with the Dell EqualLogic SR Adapter. It is supported if you are using a basic or RAW ISCSI LUN, but not with the specialized EqualLogic adapter.

From other posts the Adapter make a big difference and also functions very similar to Storage Link with a LUN per VDI approach.

Does anyone know if that is the case with 5.6+?

Thanks...

I believe multipathing is not supported for the Equallogic; you can run iSCSI over bonded pairs, but that still doesn't get you to the multipathing layer on that end.
--Tobias