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Expanded OS Support With vSphere

One of the strong points of VMware's upcoming vSphere release is support for an expanded range of guest operating systems (OS). With VI3, the current inventory of supported OSes is around 15 across various Linux, Microsoft, Novell and Sun offerings. vSphere will support more than 24 OSes. Among the new offerings include FreeBSD, OS/2, SCO OpenServer 5, SCO UnixWare 7, DOS, Windows 98, Windows 95, Windows 3.1 and DOS.

While that is a good thing in general, there are downsides. One tradeoff has to do with the potential of increased memory overhead. One of the key features enabling ESX's rockstar consolidation ratios is "transparent page sharing" technology. This technology stores memory pages that are identical across multipe VMs only once; it's effectively a de-duplication of active memory pages. Of course, more OSes in a datacenter means there will be fewer identical memory pages, and less efficient use of memory.

However, VMware has other ways to make memory more efficient, including memory ballooning. Available if VMware Tools is installed on the guest OS, ballooning moves memory from inactive VMs to active ones, which is another help for obtaining high consolidation ratios.

The other potential negative of additional platform support is the "enabling" of non-infrastructure groups to keep outdated OSes around forever. While there are legitimate needs for older OSes, such as test environments or archived systems, there is a thin line that the virtualization administrator walks in most situations regarding older OSes. It is generally a good idea to keep current on all platforms, but that is not always possible.

Is the additional OS support good news for you? Or is this something you might not want to advertise to your internal customers? Share your comments below.

Posted by Rick Vanover on 05/14/2009 at 12:47 PM


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