How to enable iSCSI multipathing with iSCSI software initiator?

[koit]

I'm trying to enable multipathing to a Dell MD3000i iSCSI target using the software initiator.

The target has 2 controllers with 2 NIC's each.

I have added every ip address on each target NIC to the "Dynamic Discovery/Send Targets" pane.

The storage view only show one path.

I have rescanned and rebooted the host severak times without any luck.

This is my config:

ESX host:

1 vSwitch with VM traffic bound to vmnic0 & vmnic1

1vSwitch with Console and VMkernel bound to vmnic2 and vmnic3

Console IP: 192.168.130.11

VMkernel IP: 192.168.130.21

DELL MD3000i iSCSI SAN:

Controller0

NIC0: 192.168.130.101

NIC1: 192.168.130.201

Controller1

NIC0: 192.168.130.102

NIC1: 192.168.130.202

Is multipathing supported using the Software initiator?

If it's supported, what am I doing wrong?

(I am aware of that the MD3000i is not official suppprted by VMware.)

Regards

Bernt Torbjørnsen

[happyhammer]

i think you will find the multipathing is not supported with the software initiator

[virtualdud3 · Accepted solution]

You can't use multipathing with the iSCSI software initiator. If you want to use multipathing, you'll have to purchase two hardware iSCSI initiators/TOEs.

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[RHTT]

Although its not strictly speaking multipathing (and cannot be control via 'manage paths') - if you have two iSCSI target ip addresses, have 2 pNICS in the vSwitch and use IP Hash as the LB method - wont the VMkernel balance the two iscsi target IP address across the two physical nics?

[virtualdud3]

I knew I should have gone with my gut, and written my first post as "you cannot have "true" multipathing"...

What you state might work (I was considering the same thing), but I'm not sure that it is worth the additional overhead. Keep in mind that you woud need both a Service Console and VMkernel portgroup for each "path"; I think you would be better off just attaching both of the uplinks to the vSwitch. When I get some more time/NICs, this would be something to play around with.

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[koit]

Thanks guys I was suspecting that the software initiator didn't support multipathing.

I didn't find that documented anywhere so I was hoping it would work.

Which iSCSI HBA is recommended in my scenario?

[dominic7]

Although its not strictly speaking multipathing (and cannot be control via 'manage paths') - if you have two iSCSI target ip addresses, have 2 pNICS in the vSwitch and use IP Hash as the LB method - wont the VMkernel balance the two iscsi target IP address across the two physical nics?

In the default case of port-based load balancing this won't necessarily help. Since you can only have one software iscsi initiator then the load blancing mechanism won't actually distribute load across both physical nics attached to the virtual switch.

I'm sure this has to be high on list of things for VMware to fix.

[virtualdud3]

I was wondering about that...That was my first thought as well. Since you can configure multiple targets for the single iSCSI initiator, I then reconsidered and now I am wondering if that might not be possible. I can't see there being any real advantages from a throughput standpoint, and obviously from a fault-tolerance perspective if the one software iSCSI initiator borks, you won't have any others. I'm curious if this would (somewhat) guard against a failure of, say, a network cable plugged-in to one of the ESX uplinks.

Then, I thought about it some more and I realized that you would have the same redundancy by simply linking multiple uplinks to the vSwitch. The only advantage I initially considered was perhaps some additional bandwidth due to the possibility (I'm still not positive it would work) of having the separate iSCSI traffic going over each respective uplink. I wonder if this configuration would even work at all, or, even if by some chance it did, if the main "bottleneck" would be the iSCSI initiator therefore since you only have the single software initiator if this would even make any sense.

If I get some spare time, one of these days I wouldn't mind geeking-around with it. This definitely isn't something I would do in production, even if it turns out that it is possible.

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[admin]

FYI. software initiator supports vmknic based multipathing, beside target portal based:

http://communities.vmware.com/thread/212653?start=15&tstart=0