How to run your business on four rack units

With a little hardware and a lot of virtualization, you can keep 50 to 100 users happy -- and you don't even need much horsepower

For the past eight months or so, I've been running a de facto virtualization test in the lab. I took a variety of lab boxes and internal servers, virtualized them on VMware vSphere 4.1, and ran them all on two physical servers. It may not seem impressive, but it indicates what's possible for small to medium-size corporate computing. And for those looking to consolidate, it's highly relevant.

These are not high-powered boxes. In fact, both servers fit into a single rack unit, using Tyan's YR190-B8228 side-by-side dual-socket server. Within that single rack unit, there are a total of four physical processors: two AMD 4162 EE CPUs with six cores apiece running at 1.7GHz, and two AMD 4170 HE CPUs in the other half of the box, with six cores each running at 2.1GHz. With 32GB of RAM in each side, that's enough horsepower for a surprising array of VMs and services.

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The storage is a Synology RS3411RPxs: a 10-spindle SATA array with redundant power and multiple 1G and 10G links, though only the 1G interfaces are in use for this particular experiment. There's a QNAP TS-EC1279U-RP in play to address other tasks, but it also contains backups of the whole shebang, replicated every few hours.

Each physical server has two gigabit links to storage and a single gigabit link to the front-end network -- small potatoes indeed. However, the services running on this cluster handle an equivalent load to a moderately sized business (50 to 100 people). Naturally, this is an estimated workload, but these boxes get pushed hard during the day and continue on with various processes in the evening.

There are domain controllers, the vSphere vCenter server, internal mail servers, external mail relays, file servers, backup servers, application servers, database servers, and even a PBX server running Asterisk that handles all the phones, both analog and SIP. It's not tasked with highly transactional databases hit by thousands of queries a second, but it's a relatively busy little data center in a box. Well, three boxes -- including the switch, it takes up all of four rack units.

In looking at the statistics over time, it's clear there are no bottlenecks anywhere for the load past and present. During normal operation, the CPUs on each server hover around 10 to 15 percent utilization with spikes to 40 percent or so when one VM gets a little more action. RAM utilization averages out around 25 percent per box; if one unit fails, there's easily room for all those VMs to restart on the other side. VMware's DRS handles the load balancing, and HA handles any hardware failure event. In fact, the only thing that could be added might be more RAM if the VM count increases to any substantial degree.

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