Yesterday, Red Hat announced the release of Red Hat Enterprise Linux (RHEL) 6. For those of us interested in virtualization, RHEL brings along many changes.
RHEL 6 promises enhanced virtualization performance in several ways. First, the operating system is now theoretically able to handle 4,096 CPUs, 16 TB of memory, and 100 TB filesystems. Naturally, these limits are theoretical, but the point is that RHEL 6 can now handle much more advanced hardware. Additionally, Red Hat claims virtualized guests are able to achieve 85 to 95% of native hardware performance. This performance comparison is for CPU-heavy workloads. I/O intensive workloads still lag behind these performance gains.
Xen vs. KVM
RHEL 6 fully does away with Xen, reflecting Red Hat's heavy investment in KVM. Although RHEL 6 can still run as a Xen-based guest, it can no longer operate as the host. Companies that have been using RHEL as the basis for their own hypervisor (Citrix comes to mind), will have to move in a new direction. Fortunately, this shouldn't be a surprise for anyone since Red Hat has been pushing KVM for quite a while. RHEL 5.4 also included KVM support.
Although Geek Run is a fairly heavy XenServer shop, we'll be evaluating both RHEL 6 and KVM. Once CentOS 6 is released, we'll start working on making that an available host option.