Since most of my work involves racked gear, usually not being removed from the rack, usually a vac or compressed air is as good as it gets.
Okay as a number of you pointed out this probably leaves a wrong impression. My intended point was that opening up and carefully cleaning a rack mounted server is basically untenable when you have twenty of them in a rack, only an hour of spare time in your maintenance window, and much of the gear needs to remain running.
Typically you don't have filters on the servers and other gear that you put in a data center, and in theory the data center's HVAC filtration maintains the environment as a relatively dust-free environment. However, we deploy gear for many years, and sooner or later it can get a little dusty anyways. People are always tracking more dust and dirt into the environment because it simply isn't a cleanroom environment.
So, first: vac is the preferred method of dealing with this, because it is least likely to be damaging to the gear, but it is also usually less effective (lower rate of airflow). When I see the inlet ports on gear getting covered with dust, a vac is the solution of choice. But as some of you have noted, ESD is a significant issue here. Dust moving along pipes gets you static, as the
woodworking guys occasionally worry about.
So you can cope with this a few ways, the expensive way is to buy a "pro" DataVac like this unit:
https://www.metrovacworld.com/DataVac_ESD_Safe_Maintenance_System-DV-3ESD1/overview
and this is a great idea if you're doing this on a daily basis. The filtering is the big thing that'd be hard to replicate, the ESD properties can probably be duplicated pretty cheaply with a small shopvac, a grounding wire, and coating the inside of your hose and tools with a
conductive paint such as this one by MG.
But those of us in the industry have a dirty little secret. Specialist gear is never available where and when you need it. We typically take a shopvac, some aluminum foil, and a wrist grounding strap. You fold the aluminum foil over the end of the hose, forming a conductive ring, and fasten it in place with the wrist grounding strap. Then you attach the wrist strap to the rack frame (or any other approperiate ground) and you're good to go.
As for compressed air, this is also a problematic realm. Compressors, by their very nature, cause moisture problems. As you compress air, it warms up, and warm air can hold lots of moisture. The water vapor then hits a cool surface like the inside of the tank or hose and condenses. In the hose this turns into fine water mist being sprayed. This problem is worse because typically we don't have huge compressors. A large tanked compressor with a relatively small draw of air means that the tank is likely to be closer to room temperature and not so able to hold moisture; in such a scenario the air tends to be naturally drier. One alternative I've seen is to use an external portable 3 gallon tank and then you fill that up and actively cool it in a fridge, then hit the drain valve. Instant tank of relatively dry air. Oil is also a problem as panz noted, the usual solution for that is filtration (or purchasing an oil-free compressor). But in all cases you still have the problem of the expanding gas cooling down as it expands.
There's been some improvement with the introduction of what are essentially fan based blowers like the
ED-500 but I haven't yet gotten around to trying one. So panz is half right and half wrong, most of us are still using strategies that involve compressors and various mitigations. But not just blasting the crappy-quality air out of a cheap compressor into your beautiful server.
