3/19    I have 2 HD's. When I transfer 25G files from one that is UDMA/5 to
        another one that is UDMA/6, it takes 15 minutes, or roughly, 27MB/sec.
        This is still well below the specifications. I'm sure that the
        100MB/sec specification is probably based on certain conditions, like
        data already in cache, sparse-data-compression, or some other ideal
        conditions that rarely exist in real life. So now I'm wondering, what
        is a typical SUSTAINED read/write rate for UDMA/5 and UDMA/6? -ok thx
        \_ The 'Ultra100' spec means the drive's connection with the system
           can do 100MB/sec.  That is not the speed of the drive itself and
           you will only see it when reading from the drive's cache.  27MB/sec
           sounds about right to me for copying.  Good drives can sustain 40-50
           MB when reading, or 30-40 when writing.  Obviously there's more over
           head when doing both at once and your drives are not say 10K RPM.
        \_ 100 MB/s is the interface speed.
           ~ 27 MB/s is the maximum sustained transfer rate of your drive(s).
           Interface speed is primarily limited by electrical signaling.
           Maximum sustained transfer rate is determined primarily by the
           data density of a platter (how many MB per square inch) in the
           drive, how fast the platters are spinning, and finally, by a
           combination of how fast the heads can seek to different tracks
           and how fragmented your files are.
           \_ FYI I my 2 HD's are on different IDE cables and they're both
              5400RPM. I wish they have a more standardized benchmarks.