Microsoft Software iSCSI Initiator with MPIO

[tao2]

Is using Microsoft Software iSCSI Initiator with MPIO installed from a guest OS supported by VMware? Can you point me to docuemntation which supports this or not?

Setup would be:

1) NetApp FAS with two Ethernet ports, two IPs and two VLANs

2) Guest OS (2000/2003/2008) with the Microsft iSCSI initiator installed/enabled and MPIO configured for either failover or load-balancing

3) Not sure how to set up the ESX network, either:

i) Two physical ESX physical NICs, connected to two separate physical switches and two vSwitches, each physical NIC on the separate VLANs mentioned in point (1). Guest OS with two vNICS, each vNIC connected to the separate vSwitches - MPIO configured to load balance/failover.

ii) Active/Passive teamed ESX physical NICs (no choice here for active/active), connected to a single vSwitch, both VLANS presented to vSwitch. Guest OS with two vNICS, each vNIC connected to the separate vSwitches - MPIO configured twith two paths to the storage.

Any other ideas would be appreciated, thanks.

[FranckRookie]

Hi Tao2,

Welcome to the forum .

An information from NetApp site: "MPIO is not supported in a guest OS." ( http://now.netapp.com/NOW/knowledge/docs/snapdrive/relsnap62/html/software/admin/GUID-5341E2D6-4BFD-41E1-8AAE-0D643D2596EC.html ).

Most of the time, we ensure iSCSI network storage redundancy via VMware network design:

• one vNic dedicated for storage in the VM

• vNic attached to a vSwitch with two physical cards in fail-over mode

Hope it helps

Regards

Franck

[tao2]

Thanks for the reply - bugger!

Why isn't MPIO in a guest supported? I can't see an issue from the storage side, so this must be a VMware limitation. Not sure why though - any ideas?

[FranckRookie]

I can't see why. Couldn't find any document neither from VMware nor from Microsoft against this kind of configuration... Will try to find one.

Franck

[Phokay]

There's no such limitation either from MS or VMware. VMware supports NPIV and iSCSI initiators inside Guest OS. Try to search with the term " iSCSI initiators inside Guest OS" for documentation. It may be in Storage Compatibility Guide.

[FranckRookie]

Hi Phokay,

Of course iSCSI is well supported in a VM. But the question here is about MPIO. I hope someone can find a document to definitely answer Tao2's question.

Franck

[tao2]

Thanks for taking an interest guys.

Just in case you can't get site of the link that Franck posted, here's an extract

ESX iSCSI initiator limitations

SnapDrive supports the use of ESX iSCSI initiators, but there are some limitations you must keep in mind.

SnapDrive does not support iSCSI session management using ESX iSCSI initiators.

You can add targets from the initiator list during LUN creation and connection.

Multipathing using both FC HBA and ESX iSCSI initiators is not supported.

Multipathing using both Microsoft iSCSI Software initiators and ESX iSCSI initiators is not supported.

ESX iSCSI initiators require RDM files to provision a LUN, but Microsoft iSCSI Software initiators do not have this requirement.

VMware limitations

RDMs are not supported on an NFS datastore; however, you can store RDMs in any connected VMFS datastore if the virtual machine is stored on NFS.

MPIO is not supported in a guest OS.

Windows Server 2008 failover clustering is not supported using ESX iSCSI RDM LUNs.

RDM LUNs larger than 2 TB are not supported.

IA64-bit operating system is not supported as a guest OS.

The second section (VMware limitations) is the key part where it states that MPIO is not supported in a guest OS. I think NetApp is suggesting that this is a VMware limitation, as I said I can't see why there would be limits from the storage perspective.

Thanks

[avarcher]

I'm as unclear as tao2 here - why is it not supporteed? If you have multiple paths from a VM, even say with multiple vNics, cant you run a piece of software in the OS to manage that?

I see the statement 'MPIO is not supported in a guest OS' is from a NetApp doc, is there a supporting VMware doc?

[tao2]

Thanks for the contributions.

As per the above post, is there any supporting VMware documentation?

Is this site moderated, some VMware contribution would be good at this point.

Thanks

[tao2]

I've spoken to someone in NetApp who says that it is supported by them and has been deployed in the field.

Read the 'restrictions' section of this doc on page 38:

http://www.vmware.com/pdf/vi3_35/esx_3/r35u2/vi3_35_25_u2_iscsi_san_cfg.pdf

Here's the extract:

"You cannot use virtual‐machine, multipathing software to perform I/O load balancing to a single physical LUN."

So if I'm reading it correctly MPIO isn't a valid configuration for a guest, though I don't understand why? Anyone?

Thanks.

[tao2]

I raised a support call and the bottom line is VMware definitely do not support third-party MPIO within a guest OS.

Support couldn't give me an answer why it wouldn't work, but it just doesn't.

I'd like to know why though :smileyshocked:

Thanks.

[glynnd1]

tao2, did VMware Support direct you towards a KB article?

[tao2]

tao2, did VMware Support direct you towards a KB article?

No, I just got this in an email:

==============================

Resolution

==============================

1) Multipathing (MPIO) is not supported on the Guest OS level as VMkernel does not understand the Multipathing on a guest level.

2) Regarding the exact VMware interpretation of “You cannot use virtual-machine Multipathing software to perform I/O load balancing to a single physical LUN".

It’s actually a bug in the documentation which would be removed in the next release.

It may just read "Multipathing is not supported on Guest level".

Thanks

[Exwork]

Regarding this line:

--- 1) Multipathing (MPIO) is not supported on the Guest OS level as VMkernel does not understand the Multipathing on a guest level.

This makes sounds like VMWare is saying you can't have the VMKernel handle MPIO for a guest. However, that's not what you asked; you wanted to run MPIO inside of the guest. The vmkernel isn't involved here.

I don't know about "supported by VMWare", but you can definitely install MPIO drivers inside a Windows guest, and run MPIO to an iSCSI SAN. I've been doing this for years.

[Phokay]

@ Exwork,

Running iSCSI one thing but getting MPIO working is another. If you enable iSCSI MPIO inside the guests, Windows for instance, you will get multiple LUNs show up with single path each instead of single LUN with multipath. This the problem.

[tao2]

I think what VMware were getting at is that the VMkernel actually manages the switching of IP traffic at the vSwitch level. So the VMkernel is involved to an extent and this is where the issue of supporting MPIO comes in.

Thanks

[RVJE]

Well I'm running MPIO iSCSI from within my guest OS, and it seems to be working fine. Don't know why i should'nt work as long as you place each NIC i separate vSwitches.

/Rasmus

[FranckRookie]

Hi All,

I think we all agree on the fact that it should work. But as it is not supported, do you want to put it in production knowing that, in case on an issue, you will not get help from VMware?

I will continue to use redundancy functionalities from virtual network design.

Regards

Franck

[RVJE]

No, not really. At the time I build my setup, I could'nt find any document that suggested it was'nt supported. All the consultants I asked, and the forum posts I read said if was fine. Which is quite annoying, since I have to rebuild my installation, if I wanna receive support.

VMware said that it would'nt work, I'm just saying it does work.

/R

[tao2]

What confuses me is that this is quite a commom and accepted setup. It needs more than just a vague, subtle line in a VMware PDF to suggest that it is not supported.

[RVJE]

I agree. And moreover I think that VMware should think more iSCSI into their design, the reason I used MS ISCSI instead of VMwares iSCSI, was that I needed MS Cluster Services, and vmware does not support MSCS over iSCSI. But since MS does, and vmware supports iSCSI from the guest, it was the perfect sollution for me. Except of couse, that they apparently does'nt support MPIO..

Sucks.

/R

[Exwork]

That's going to depend on your version of Windows, and how your storage array functions.

With some of my arrays, I can use the native multipathing driver for Windows 2008 to run MPIO.

With others, I need to install a DSM into the OS to properly multipath.

Not all arrays expose multiple paths by default - for example, Lefthand and Equallogic use a single VIP.