1. It's Cheap
It doesn't have to cost more than $250.
2. It Has a Solid-State Disk Drive
Hard Drives are mechanical devices that come in two forms: the ones that have failed, and those that haven't failed yet. Many netbooks come with solid state drives that potentially last as long as the rest of the computer electronics. If it doesn't come with an SSD originally one can be added later on, often in the form of a Compact Flash adapter.
The newly released Intel X25-V is an SSD especially targeted for netbooks, and sells for around $120.
3. It Has Built In UPS and Power Management
Since it's a netbook, it obviously has a battery. This saves you the need for a UPS system to keep the system running in case of power failure.
4. It Has a Built In Console
Servers are typically "headless", i.e. used without a monitor and keyboard. These can however come in handy for installation or troubleshooting. Having a server with a built-in console can be very useful and saves the cost of expensive remote Keyboard, Video, Mouse (KVM) solutions.
5. It Has Built In Thermal Management
Because of their small and compact form factor, portable computers come with built in thermal management features that often are more elaborate than a typical server. They are also built to be used in a "normal" living room environment, and not a server room with ample cooling.
6. It Has Backup Connectivity
Many netbooks come with a bundled mobile internet device in addition to wireless and wired ethernet. This provides a useful backup connectivity solution in case the primary connection fails or is congested. Combined with the built in battery this will keep the server running and accessible even if the building has lost all electricity, a feature that would be very costly for a full fledged server.
7. It's Small And Quiet
Servers are not build to be quiet. A 1U rack-mounted server typically has around ten 1-inch fans, and boy are they noisy! They typically will be kept running at full speed or a minimum speed that is still very noisy. Noise level ratings around 50-60 dB are common, or as noisy as a TV set or an air conditioning unit. Laptops are much quieter.
8. You Don't Need More Performance (At Home)
A home server is typically either a simple web server or a server to make files available. It thus does not need to be very powerful. The $250 price point above gives you a 1 GHz Atom processor.
9. You Don't Need More Space
It's for sharing documents or services that depend on being at your home. With a 16 GB or 32 GB SSD you easily outperform all but the most expensive hosting or sharing sites. Add in an SD card reader and you can easily expand this storage space at almost no cost.
10. Spare Parts Are Cheap(er) And Easier To Obtain
Server-grade replacement parts are typically pricey and not on stock in your everyday computer store. Laptop spares on the other hand are stocked everywhere. For most popular models replacement batteries are manufactured by other vendors long after the original battery has gone out of distribution. I just bought one for my nine-year-old model.
11. It Doesn't Have to Be New
You can get good deals for used laptops on eBay. My home server was actually purchased there for $120 in 2006, then five years old. It's still running fine.
And since it's a home server you can migrate easily your server farm if you move from your house!!
SvarSlett