IBM, VMware Cooking Up vSphere 4.0 Support for i

September 28, 2009 Timothy Prickett Morgan

The word on the street is that the software engineers at the Power Systems division at IBM and their counterparts at X64 hypervisor juggernaut VMware, are working to get the new ESX Server 4.0 hypervisor–and perhaps many of its vSphere 4.0 extensions–integrated with the i platform. But don’t hold your breath. This will apparently take some time.

As all i shops are well aware, Windows is by far the preferred alternative platform at AS/400, iSeries, and i customers, and tends to be used on infrastructure workloads such as Web, print, and file serving, or as application servers with Java and C# applications smacking against DB2/400 databases stored back on the i box. But i boxes have another more direct link to Windows boxes, and are often used as external disk arrays for external Windows servers. IBM has more or less killed off its internal x64 server cards and since May 2006 has been pushing iSCSI links between external System x servers and internal disk arrays on System i and now Power Systems i boxes. With this link, the external Windows boxes see the storage on the i box as a giant C: drive, and customers can gang up multiple Gigabit Ethernet links between the servers and the i machine to boost the I/O bandwidth of the links connecting the two machines using the iSCSI protocol.

Then along came X64 server virtualization, adding another layer of complexity to this hybrid Windows-i storage setup. VMware’s ESX Server hypervisor, just like any operating system, wants to control processors, memory, network, and disks for any physical machine it is hosted upon and on which it, in turn, can host multiple virtual machines and operating systems atop ESX Server. Two summers ago, with OS/400 V5R4, VMware and IBM finally rolled out support for VMware ESX Server 3.5 to see i disk arrays as suitable storage for ESX Server and its guests, thanks to iSCSI drivers from QLogic that were embedded in the hypervisor.

At the time, IBM had VMotion live migration of X64 guest operating systems using iSCSI links back to i-based storage running in the labs, but wanted to take more time to test it. When i 6.1 was launched last in April 2008, shared storage was supported (unlike in OS/400 V5R4 officially), according to this IBM document, and that meant that VMotion live migration and other high-availability add-ons for ESX Server also worked when using an i box as a glorified disk drive.

So everything was rosy and peachy keen right up to the point where VMware launched ESX Server 4.0 and its vSphere 4.0 add-ons in April. The software didn’t start shipping until the end of May, and is being put through its qualification paces at many midrange and enterprise shops. But right now, IBM’s iSCSI links are not compatible with ESX Server 4.0. That means customers are stuck on ESX Server 3.0 or 3.5, which is more expensive and has fewer features.

The word that I hear on the street is that IBM is hoping to get its iSCSI links working with ESX Server 4.0 by sometime early next year; it could be in the spring, and one source even pinned it down, saying that this iSCSI support for ESX Server 4.0 instances will come out with i 7.1 in April 2010. I have also heard from a source familiar with IBM’s plans that this updated iSCSI support for ESX Server 4.0 will be back-ported to i 6.1 through PTFs. This might mean that such capability is already available in the labs in Rochester if you need it, and that it could roll out as PTFs well ahead of next April, if that is indeed when i 7.1 is expected.

The delay apparently has something to do with the way VMware is having the new ESX Server 4.0 hypervisor talk to iSCSI storage. In the past, I am told, IBM used features on iSCSI adapters to initiate the link between ESX Server and i storage, but now VMware wants this link initiated through software only. Everything has to be virtual–a lesson that some people at IBM learned more than 30 years ago with the System/38.

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