Updated: What's the deal with EMC CX arrays not supporting VAAI with vSphere 5.0?

(If you have read this post before then skip to the bottom for recent updates)

We are in the process of upgrading our production environment to vSphere 5.0 U1. A new vCenter 5.0 server is already in place, and we attached the production ESXi hosts (that are still on 4.1 U2) to it.
The next step would be to upgrade the hosts. In the meantime, since this is a qualified production environment running more than 1.500 virtual servers I became a bit paranoid about hardware and software/firmware compatibility, and decided to double check if the environment is fully supported (or if we should upgrade any firmware first). I was pretty confident that we are on the safe side because we never had any issues with vSphere 4.1 and always kept the environment up to date.

But then I stumbled over this VMware KB article: EMC CX and VNX Firmware and ESX requirements for vStorage APIs for Array Integration (VAAI) support. It states that ESXi 5.0 does not support VAAI on our Clariion CX4 arrays even although they have the latest FLARE code:

	vSphere 4.1	vSphere 5.0
CX4 Series Flare 30/29/28+	VAAI Supported	Not Supported
VNX Series OE 31 or Later *	VAAI Supported	VAAI Supported

I checked the test hosts that we already updated and they showed VAAI being supported on the CX4 LUNs in the vSphere client. However, the KB article recommends to disable VAAI on these hosts ...

I quickly searched the Internet for relevant posts and statements and browsed through the VMware Community forums. There I found this post where people complain about the VAAI status shown as unsupported. It looks like there are dependencies to the LUN size (smaller or larger than 2TB) and to the array's failover mode (sounds like you need to use ALUA / failover mode = 4 which we are already using). But from this post I get the impression that everything is fixed with the latest 30.x FLARE code releases).

We contacted both VMware and EMC to get some clarification now, and I will keep this post updated with any new information. In the meantime I ask everyone using ESXi 5.0 with EMC CX storage to comment on this post whether you are using VAAI, if you have any issues with it, and what FLARE code you have on the arrays. BTW, you can check what VAAI primitives are in use with your storage LUNs by running the following esxcli command:
   esxcli storage core device vaai status get

Thanks in advance for any helpful comments!

---

Update (2012-05-20): I got some feedback from other users, VMware and EMC on this issue, and used my best Google-Fu to get related information about vSphere 5, VAAI, VMFS-5 and/or EMC CX support. Here are the results (somewhat unsorted):

• Several users use this unsupported setup, but do not have any issues with it (so far).
• pape pointed to some useful VMware KB articles in the comments of this post. Here is an overview of these and some more related articles:
• KB2006858: ESXi 5.0 hosts fail to mount VMFS5 volumes that are formatted with ATS-only capabilities (describes an issue with VMFS-5 volumes and ATS locking seen on EMC arrays, but this is solved with ESXi 5.0 Update 1)
• KB1033665: Disabling the VAAI functionality in ESX/ESXi
• KB2012967: Disabling VAAI functionality for a specific array (Now that would be interesting, but the link doesn't work as of now)
• KB1021976: vStorage APIs for Array Integration FAQ (this FAQ also covers differences in ESXi 4.1 and 5.0 resp. VMFS-3 vs. VMFS-5)
• KB2003813: vSphere 5 FAQ: VMFS-5
• The following VMware blog posts of Cormac Hogan are interesting in the context of VAAI usage with VMFS-3 vs. VMFS-5:
• vSphere 5.0 Storage Features Part 1 - VMFS-5
• vSphere 5.0 Storage Features Part 3 - VAAI
• VMFS Locking Uncovered (About the improvements that were made with file locking during VMFS evolution)

Regarding my specific issue (lack of official support for VAAI with EMC CX arrays and ESXi 5.0) I finally got one really detailed and helpful comment from an EMC representative: EMC tested the VAAI functionality of ESXi 5.0 with their EMC CX4 arrays (I specifically asked for the CX4). It has been "tested as functional", but it only passed the certification tests of the ATS and Zero primitives, but failed the certification test of the XCopy primitive.
I wonder why this happened, because VAAI was fully supported with ESXi 4.1 (i.e. it must have also passed the XCopy test), and with ESXi 5.0 there were no changes to the XCopy primitive (at least I could not find any information about such a change).

Anyway, this is probably the reason why EMC and VMware do not officially support VAAI with ESXi 5.0 on CX arrays. From a customer's point of view this is disappointing, but from EMC's point of view this decision is understandable, because they want to focus on their current products and not waste support resources on somewhat outdated arrays like the CX ones. However, according to this EMC representative it may be possible to come to an individiual support agreement with EMC and VMware (EMC calls this RPQ = Request for Product Qualification) if you nevertheless must or want to have an official support statement for whatever reason.

I also had the idea of disabling only the XCopy primitive to be on the safe side, but I don't want to do this globally, because we also use a fully VAAI supported VNX array with our production hosts. So I was glad to find a link to the promising KB article KB2012967 (see list above), but this link currently doesn't work. I will ask VMware about this ...

---

Update (2012-06-20): In the meantime an EMC representative confirmed to me that all three VAAI primitives work fine with vSphere 5.0 and CX arrays, and that they even support it, but you need to file an RPQ with them in order to get formal support.

We have this configuration (VAAI turned on for both our CX4 and VNX arrays) running with vSphere 5.0 in production for about 6 weeks now without any problems.

The link to VMware KB article KB2012967 still doesn't work, but it is now listed to as being "[Archived]" in the reference section of KB1033665 ...

---

Update (2012-07-11): It turned out that you no longer need an RPQ with EMC. They now officially support the vSphere 5's VAAI implementation on the CX4. The combination is listed in their latest Simple Support Matrix for VMware vSphere 5 (Powerlink account needed for download):

Snippet from the EMC Simple Support Matrix for vSphere 5 (of July 2012)

VMware though does still not officially support it (KB2008822 is unchanged as of today). In another blog post I already explained the reason for this.