If you're using VMware ESX extensively but haven't begun monitoring resource consumption and available capacity, you will lack valuable ammunition come budget time. Usage measurements can justify infrastructure expansion, help recover costs, and even transform IT into a profit center.

The VKernel Capacity and Chargeback Virtual Appliance is ESX-specific software that reports on capacity and resource consumption. It provides chargeback totals based on a user-defined unit cost for four core metering sources: CPU, RAM, storage, and network usage. An unlimited number of custom fields are available for monitoring cooling costs, administrative services, software licensing, or whatever else you can dream up. VKernel says the product can handle as many as 300 hosts, so there's room to breathe.

Provment, VAlign Software, Vizioncore, and Xentro sell chargeback services for virtual environments, but none offers a virtual appliance. Why does that matter? Like a physical appliance, a virtual appliance is prepackaged and preconfigured to deliver functionality with minimal setup, saving time, money, and your sanity. Just import it onto a single ESX server in your cluster or into VMware Workstation or GSX and fire it up. You still will need to declare ESX hosts to monitor, create logical virtual machine groups, and define unit costs for metering.

THE VIEW FROM ABOVE

You've likely heard all about the resource consolidation, machine isolation, and increased security benefits of virtualization. But less publicized is the fact that virtualization may improve your ability to view capacity and consumption stats, especially handy for IT shops that want to assign dollar values to resources used by business units.

The VKernel virtual appliance is a VMware-based virtual machine running on SUSE Linux Enterprise Server, with MySQL, Apache Tomcat, and an Ajax app server bundled. It works only in VMware environments, and it monitors only virtual machines on ESX host servers.

VKernel's functionality is based primarily on a concept called the "business service." Business services are containers for capturing aggregate values among groups of virtual machines that either provide a single service, such as e-mail, or that differ in functionality but comprise a particular distributed application or business process. The "customer" concept is used to generate chargeback reports, and each customer can have multiple associated business services. You define unit costs for CPU, memory, storage, and network in predefined or custom increments.

VKernel constructs chargebacks for each resource type or business service by taking a daily average of resources consumed, then averaging those values over the chargeback period.

VKernel says future iterations will allow more precise consumption measurements for instances where you need to know totals, not averages, as with power or administrative costs.

VKernel provides default resource pricing as well as a simple mechanism for IT to tally its own expenditures. The reporting capability is fairly robust. You can generate reports on the fly or automatically at specified intervals. VKernel's Web site has examples available for download.

Note that full monitoring will consume about 341 Kbytes per VM per day. If you have 50 virtual servers, your database will eat up nearly 6 Gbytes of disk space yearly--and that's in addition to the default 1.1-Gbyte appliance size.

While VKernel provides shell scripts to help archive all that historical data, this is one feature that could use improvement. For example, we'd like to have archiving fully integrated into the appliance as part of the GUI.

VKernel says its virtual appliance won't degrade performance of your cluster. An early beta release did exhibit some degradation, but the company says this issue has been resolved.

VKernel 1.0 is available now as a 350-Mbyte compressed downloadable file. Pricing is $495 per CPU socket, per monitored host server, so if you have a three-server cluster, each with two sockets, you'll pay $2,970 in licensing. That includes the first year's support. Thereafter, the standard 20% support fees apply, yielding a $594 operating cost in the second year and beyond.