I've used serviceuptime, hyperspin, and pingdom. I don't like pingdom as I get a lot of false results that don't show up on serviceuptime or hyperspin. Right now we're using serviceuptime and we like it a lot.
Yep, however a recent poll showed results in favor of compaq with 32% poll, and IBM having 27%, whereas HP secured 21% for being the most reliable server.
Thanks for the advice personally I think dell are probably the cheapest. Reliable not too sure. HP is expensive and moderately reliable.
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Having used SuperMicro, Dell, HP, and IBM servers in mass, the best experience that I've had by far was with Dell. Near zero failure rate, fantastic warrantee, and their chassises are a dream to work with. This was primarily on high-end servers though... I don't think that prices/models make any sense at all with them if you're looking for lower/end systems.