I can get some decent deals on eBay for rackmount servers (described as, for example, '2U rackmount server') that I'm looking at to replace my Synology NAS.
Would I be able to just buy this 2U server and sit it under my desk somewhere, or is it a requirement that you absolutely have to have a rack to put it in?
What does a rack give you that sitting it on its own somewhere does not?