10 things to look for in a KVM switch

By Erik Eckel | April 5, 2011, 1:49 PM PDT

IT professionals spending any significant time in server rooms know the importance of good quality keyboard/video/mouse switches. Plagued with a poor performing KVM switch, even mundane tasks — such as cleanly rebooting systems, confirming successful backup operations, downloading and installing OS updates, and completing general troubleshooting routines — become needlessly complicated.

Whenever you buy a new KVM switch, you want to make sure it meets your requirements. Review this list to avoid common errors many rookies or budget-minded organizations suffer when selecting a unit too quickly or without performing the necessary homework.

1: Proper operation

Little in IT is as frustrating as not being able to properly view a critical system or connect using a standard keyboard or mouse, especially as the issue seems to arise at the most crucial times (an email server is down, the Internet has failed, hundreds of users are affected, etc.). When you're combating a stressful failure or outage, that's no time to have to fumble around with a flaky KVM.

Perform some due diligence. Whenever you think you've found the perfect KVM, search Internet forums and read Amazon, Newegg, and other reviews to learn what others' experiences have been using the same model. If feedback is positive, you're good to go. But if proper operation in the real world proves troublesome, keep searching.

2: Compatibility

KVMs often work with most operating systems, but occasionally glitches arise. Review a model's specifications to make sure it's compatible with the operating systems it must support. If you don't, you'll have to box everything back up, request an RMA, and send it back.

3: Required connections

I've seen seasoned engineers purchase new KVMs that support only DVI video connections or only PS/2 peripherals, then discover the servers all have USB- or VGA-only connections. In other cases, engineers assume that the model they're buying provides KVM over IP support, when it doesn't.

Don't order a KVM switch haphazardly. Confirm that models support the connections in place, which may require a quick-and-dirty audit of current equipment prior to ordering, especially when equipment from multiple locations is being combined in a single site for the first time.

4: Port expansion

Shortsighted administrators often purchase eight-port KVM switches when they need to support eight servers. Whenever possible, purchase KVM switches with additional capacity. Unforeseen but reasonable decisions to add a VOIP system, new database platform, HVAC- or alarm-controlling servers, and other devices instantly place you at a deficit. Too often, organizations end up with more systems than ports; if possible, purchase KVM switches with 20% to 25% extra ports.

5: Onscreen display

Onscreen displays (OSD) and menus are kind of like rear-window defrosters — you don't miss them until you don't have them. They provide visual indications of which systems are online or connected, making it easier to configure settings and switch between systems. If you're accustomed to working with GUI assistance, select a model that supports OSD. Also consider OSD-enabled KVM switches if you have to switch frequently between numerous systems, as OSD will make you more efficient.

6: Mount options

Desktop KVMs work well within many organizations, but they don't work well when migrated to server racks. In businesses experiencing growth but working without a current server room or even half-rack, look for KVM switches that can be converted to rack mount, should the need arise. Or start with a standard rack mount unit. Select desktop models only if you're confident the unit will never end up servicing systems mounted in a professional rack or cabinet.

7: Electrical power

KVM switches with their own power supply work more consistently, in my experience, than do those that draw their electrical supply from the systems they connect to. Even many budget-priced KVM switches include optional power supply connections but don't ship with a standalone power adapter. Always check to see whether a power adapter is included with, or supported by, the unit you select. If no power supply is included, visit a nearby Radio Shack or electronics store to purchase the missing component, after assuring its compatibility.

8: Sufficient cable length

More than once, I've seen six-foot KVM cables prove too short when wound through cable management infrastructure. As part of a pre-purchase audit, measure the distances the KVM's cables must cover. Ensure that included cables, or those you purchase separately, are long enough to span the required distances. It sounds academic, but KVM cables are expensive, even when purchased in bulk, and they are painful to have to rerun in server cabinets after discovering the just-purchased items are too short.

9: Reset button

Occasionally, KVM memory becomes corrupted. Since KVMs frequently receive power not only from a standalone power adapter but also from the systems the KVM switch is connected to, it can prove difficult to clear a corrupted KVM switch's electronics. No one should have to climb behind a server rack to physically disconnect four, eight, or even 16 systems just to clear a frozen KVM. Look for systems that have a simple reset button.

10: Audio support

While less common, some environments require that system audio be available from the systems the KVM controls. Of course, not all KVM switches support audio. Review a specific model's individual specifications to confirm that it will support audio. Otherwise, you could find yourself stuck with convoluted workarounds resulting in a cacophony of noise. Prevent headaches. KVM switches can be very unforgiving. Perform your homework up front

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