Guild Companies

VMware, which has a bunch of different products to create virtual partitions on Intel-based workstations and servers, has been showing off a new add-on to its ESX Server virtual machine middleware that allows virtual partitions on ESX Server to span two processors, instead of being confined to one. This may not sound like a big deal, but it is incredibly difficult to do. It is much easier to carve up a single processor into many virtual machines than to make a virtual machine span more than one processor.

The forthcoming Virtual SMP add-on to ESX Server will be available sometime in the second quarter. Sources say that pricing for Virtual SMP has not been set. ESX Server is a special low-level, hypervisor-type partitioning program that sits between operating systems and the Intel server iron that completely isolates partitions from one another. It is VMware's flagship product, and it supports up to 64 virtual machine partitions and a total of 64 GB of main memory, which can be carved up into individual machines. ESX Server lets instances of Windows and Linux operating systems sit side by side on an Intel server, with each virtual partitioning functioning more or less like a stand-alone, isolated server. By contrast, the company's GSX Server creates virtual partitions within an existing operating system--much as a DOS window creates a virtual machine within the Windows environment. The virtual machines in GSX Server can be hosted on Windows or Linux servers and ride on top of that primary operating system; the resulting virtual machines can be loaded with Windows (server and workstation versions), Linux, or NetWare.

While this virtual partitioning capability that spans two processors is going to make ESX Server more useful for supporting multiple application and database servers consolidated on big iron, Virtual SMP is still not as sophisticated as the logical partitioning capability that IBM offers in its OS/400-based iSeries line. This logical partitioning can span as many as 31 processors for a single partition, and allows for very fine granularity for partitions on a single processors, with up to four OS/400 partitions and 10 Linux partitions per processor. IBM is porting this logical partitioning capability to the pSeries line and will announce a whole new hypervisor-based partitioning scheme in early 2004 that could allow hundreds of logical partitions on a single 64-way Power5-based "Squadron" server. The future Squadron servers will run Linux, OS/400, and AIX in logical partitions, and OS/400 and AIX will be able to run the entire machine, too, because their operating systems can scale to 64-way SMP. Linux pretty much tops out at eight-way processing, and that is not going to change with the Power5 servers, which means a big Squadron box will be able to house eight or more Linux partitions.

The next logical step for Virtual SMP is to span four and then eight processors, which would allow ESX Server to create virtual, isolated four-ways and eight-ways inside future 32- and 64-way Intel-based servers. Sources at VMware say that the company is working on four-way Virtual SMP, but they concede that if going from virtual machines that span one processor to two processors is hard, spanning four processors is even harder, because of the cache coherency and other timing issues. It seems reasonable that an eight-way Virtual SMP would be even harder. But if enough people start clamoring for it, you can bet it can be done. VMware will do it, before Microsoft's new Connectix unit does it.