Database Sizing Charts for vSphere 4.0

Many of our customers have databases running on proprietary hardware that is approaching end of life. Often these databases are not considered as candidates for virtualization due to the fact that they are running on larger systems with more sockets while x86 systems have fewer cores and virtual machines often have even lower vCPU limits. Advances in processor technology however often place the performance of a VM with a smaller number of virtual processors at par with a lot of these much larger systems.

In this document, we introduce capacity planning and sizing charts for databases in a virtual environment. The purpose of these charts is to aid in sizing of databases which are being moved from a legacy RISC based physical machine to virtual machine running on a modern x86 based system running VMware vSphere.

We combined a set of data from both experiments in the lab and published throughput results to derive a VMware conversion metric from older RISC machines. The data should be used to identify potential candidates of database servers which can easily be virtualized, and to then perform first order sizing for those virtual machines.

The following table provides an estimated capacity planning reference for aggregate database throughput compared to the performance of a virtualized database running on a reference system.

The reference system used for this chart is an Intel Nehalem 2 socket 8 core system, as measured in the in the “Virtualizing Performance Critical Database Applications in vSphere 4” paper. The reference system has a VMware DBunit throughput of approximately 1000 per core, for a total capacity of 8000 with 8 cores. We’ve assumed near linear scalability in the first version of these tables.

The table may be used two ways:

1. To calculate if the largest VMware virtual machine is large enough to accommodate the database from the physical RISC system.  The “Number of RISC Processors…” column shows the number of sockets in the largest system that an 8-vcpu VMware VM can replace for that machine type. Items denoted with a * indicate that the virtual machine is larger than the biggest physical system for that range.
2. As a sizing estimator. “VMware DBunits” is the number of processing units needed for each RISC CPU in the source physical system. To calculate how many virtual cores are required to replace a physical system, simply multiply the number of processors (sockets) in the physical system by the DBunit score, and then divide the result by the processing capacity of the reference core (1038 for our Nehalem reference system).

As an example, a Sun E1290 system with 8 1.5Ghz USIV+ processors would require a DBunit of 8 x 723 = 5784.  Rounded up, this would require a virtual machine with 6 cores, thus a 6-vcpu VM would be required for equivalent processing capacity and headroom.

More often than not, the physical system is less than 100% utilized, because significant headroom is required. With virtualization, much less headroom is required, since if the virtual machine needs more processing capacity, it can simply be reconfigured with a larger number of processors. If we assume that the source physical system is at most 35% utilized, then we can run the same database in a virtual environment using only 2024 units, which is accommodated by 2-vcpus.

This is the first public version of this table. I'll update it as we gather more information and feedback on its use.

Table of RISC Throughputs
compared to a virtual machine (Version 1.1, April 2009)

* Capped by
max physical CPUs supported by system