lphillips@lpami.wimsey.bc.ca (Larry Phillips) (09/29/89)
In <3945@m2-net.UUCP>, ba@m2-net.UUCP (Bill Allen) writes: >What is the real value of a hard drive's MTBF (Mean Time >Between Failure) rating? "For comparison purposes only?" >"Your mileage may differ?" Are these MTBF ratings guessed >at by the manufacturers themselves? Yes, they guess, but bear in mind that the guesses are fairly educated, based on their knowledge of the materials that go into the drive, past experience, and some testing. As with anything, the disclaimers are necessary. Why does ont light bulb burn out in a week, while another one from the same box lasts months, or perhaps years? The manufacturer cannot make every unit exactly the same as another; flaws will show up in any part of the unit, and can be undetectable short of destructive testing. Even if two units are identical, outside influences will cause wide variations in the lifetime of any given unit. Heat, vibration, handling, static, moisture, voltage variations, magnetic fields, altitude, and so on, will all have their effects, sometimes during the journey from the manufacturer to the end user, some after installation. >Seagate's ST???N SCSI series is shown as 70,000 MTBF >(source: text files on Seagate's own BBS at 408-438-8771). > >Micropolis SCSIs 150,000MTBF (source: Oct '89 Computer >Shopper, p.483, Hard Drive International ad, 800-234-DISK) > >Can I compare quality? life? durability? this way? Only if you know the exact conditions that the MTBF is in reference to; only if the MTBF is accurate (without the sales department influencing the figure); and only statistically, not on an individual unit basis. You could take two drives, each having widely differing MTBF figures, and you could lose both of them the first time you apply the power, or they might both run for 30 years. With these caveats in mind, the two drives you mentioned may be judged loosely, based on the figures. On the other claw, will you really care much if a 40 or 60 or 100 meg drive lasts 8 or 17 years? Will you be likely to have replaced it with that Whizzbang 40 Gigabyte floptical drive by then? -larry -- The Mac? Oh, that's just like a computer, only slower. +-----------------------------------------------------------------------+ | // Larry Phillips | | \X/ lphillips@lpami.wimsey.bc.ca -or- uunet!van-bc!lpami!lphillips | | COMPUSERVE: 76703,4322 -or- 76703.4322@compuserve.com | +-----------------------------------------------------------------------+
ba@m2-net.UUCP (Bill Allen) (09/29/89)
What is the real value of a hard drive's MTBF (Mean Time Between Failure) rating? "For comparison purposes only?" "Your mileage may differ?" Are these MTBF ratings guessed at by the manufacturers themselves? Seagate's ST???N SCSI series is shown as 70,000 MTBF (source: text files on Seagate's own BBS at 408-438-8771). Micropolis SCSIs 150,000MTBF (source: Oct '89 Computer Shopper, p.483, Hard Drive International ad, 800-234-DISK) Can I compare quality? life? durability? this way? -- --------------------------------------------------------- Reply-To: ba@m2-net.UUCP (Bill Allen Beogelein) M-NET, Ann Arbor, MI or call Sharewarer's BBS at 313-473-2020 24hrs, PCP thru MIDET, 100% Amiga ---------------------------------------------------------