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RISC to x86, Physical to Virtual

Many of the virtualization customers I speak with have been asking about what database can be virtualized, so I typically present a green, yellow and red set of criteria to help guide the process. We typically look at I/O rates, SMP width and capacity of the source physical system as a guide.

Recently, we were able to run a full TPC-C like workload inside a virtual machine, showing that we can run at over 90% efficiency, even given the brutal nature of this workload (it’s I/O rate is actually about 6 times higher than what you would typically see in a customer workload).

The methodology is that green is considered for the easy databases — typically 2 CPUs or less and less than 500 disk I/O’s per second. These virtualize easy, with minimal best practices required. Yellow is for larger databases, where the I/O rate is higher — they typically need more care and attention to the way the storage is provisioned underneath the virtual machine. For example, if the database needs 1,000 IOPS, then it should be on a disk or LUN with at least 10 disks backing it, to provide the necessary I/O throughput.

Red is typically when you have a database which is much larger than the limits provided for by a virtual machine — e.g. the maximum amount of memory or number of virtual CPUs possible.

That got me thinking — now that vSphere 4.0 (the new name for VMware’s full virtualization offering) we have three things happening at once — greatly improved database efficiency, a now-wider SMP virtual machine (SMP up to 8 virtual CPUs), and the increased throughput of the new Intel Nehalem systems. That combined, we have enough throughput to run some of the larger databases — often hosted on larger RISC machines.

Since it’s a database system, it’s relatively easy to migrate from SPARC to x86, given that there is an x86 equivalent for the OS (e.g. Solaris or Linux) and the database (e.g. Oracle).

By taking a composite metric of several different benchmarks, we can create a capability mapping chart between different RISC CPUs and the performance that we see inside a virtual machine. Some of the data may be surprising — some of those large older SPARC machines can now fit into a virtual machine on the newer x86 systems.

The first version of the table is over at the VMware performance blog.