Apple uses the term "server grade" in its description of the hard disk in the Time Capsule. On Monday, The Register discussed a Time Capsule that was taken apart, and Tony Smith concluded that the term may be used somewhat loosely.

One buyer who took his Time Capsule apart and provided photographs noted that it contained a Hitachi 1 TB Deskstar 7K1000, model HDS721010KLA330, designed for "networked storage servers." However, Hitachiis caveat is that, unlike the higher level model designed for rugged 24x7 server use, namely the Ultrastar A7K1000, the model in the Time Capsule is designed for "lower duty cycle environments in the enterprise storage hierarchy."

At Tidbits on Monday, it was reported that Apple senior product manager Jai Chulani said "server grade" means "the same 7200 rpm drives used for Appleis Xserve servers, and that they have a higher mean time between failure (MTBF) rating than consumer drives." That MTBF for "server grade" was placed at 1 million hours.

Mr. Smith at The Register noted that the technical term "server grade" lacks a standard definition, but felt that such a term, in his opinion, belonged to a drive more rugged than Hitachiis Deskstar.

In his blog on Saturday, Victor Cajiao agreed and pointed out that the Deskstar data sheet declines to provide an explicit MTBF number, something that server grade drives, like the Barracuda ES.2 drives, typically do.

In any case, it seems that Appleis industry term, intended to convey a simple idea, is getting some close scrutiny from observers. Not helping matters is the generally recognized idea that drive manufacturers themselves use estimation methodologies for MTBF that is regarded as optimistic. Despite that, higher MTBFs are still better than lower MTBFs -- at least when users get to know what they are.