Virtualization makes many elements of IT management easier, primarily due to newfound server portability. However, disparate licensing terms amongst enterprise ISVs and OSVs has led to both confusion and frustration for many IT pros.
Today, virtualization is simplifying server management; however, a consequence to virtualization should not be licensing complexity. Servers are heading down a path toward a mobile infrastructure that's free of hardware dependencies. So when it comes to virtualization, vendors need to be clear in their support and provide explicit licensing terms for virtualized environments.
Novell is clearly a leader when it comes to virtualization licensing. Here is a portion of the Novell SUSE Linux Enterprise 10 license:
While each physical server requires the purchase of a subscription to be activated and receive ongoing updates and patches, an unlimited number of virtual server images can be created in Xen or other virtualization technologies on each activated physical server. No additional subscriptions are required for virtual images.
So for SLES 10 virtualization deployments, licensing is simple. Just count up the number of physical servers that will run SLES 10 VMs and that's the number of licenses that are required. The total number of VMs is irrelevant.
Microsoft also allows unlimited VMs to run on a physical host, but only if Datacenter Edition licenses are purchased and applied to each physical server. Organizations with volume licensing packages already in place would have to purchase additional Datacenter server licenses to meet the Microsoft licensing terms. VMware has been quick to highlight the complexities of Microsoft licensing in relation to virtualization. If you haven't already done so, I would recommend reading the following two VMware white papers:
- Microsoft Virtualization Licensing and Distribution Terms
- Addendum to Microsoft Virtualization Licensing and Distribution Terms
Of the many licensing issues noted by VMware, the licensing implications for live migration (or Vmotion) is most significant. Organizations that do not purchase Datacenter Server licenses will have to contend with the following:
Reassignment of a license to another server is only allowed once per 90 days except in case of hardware failure. - Licensing Microsoft Server Products with Microsoft Virtual Server and Other Virtual Machine Technologies, October 2006, p. 12
Live migration is often used to relocate VMs in order to perform scheduled maintenance on a physical server. Limiting VM movement to once per 90 days forces organizations to purchase Datacenter Server licenses just to be able to use the live migration features of their virtualization platform. Note that this policy does not impact Microsoft's current (Virtual Server) and planned (Windows Server Virtualization) platforms, since live migration is not supported and was recently pulled from the forthcoming Windows Server Virtualization (Viridian) service.
Microsoft's Datacenter Server licensing policy (allowing unlimited VMs per physical host) was a good first step. However, this does not help organizations that intend to transfer existing server licenses to VMs as part of a physical to virtual migration project. As an industry leader, it's very likely that if Microsoft took strong steps to simply its OS and application licensing in support of virtualization, many others would follow.
Novell should be applauded for its progressive licensing, but other leaders are needed. Vendors unwilling to take the initiative to develop a virtualization licensing policy can be compelled to do so by the user community. RFPs are pretty powerful documents, and by including virtualization support and licensing requirements in all RFPs, organizations will be able to pressure both ISVs and OSVs to bring about change.
post by: Chris Wolf