[rescue] Sun 711

[George Adkins]

> > don't see how that would falsely affect this test since it's straight
> > read performance (no write caching).
>
> For large sequential reads the storage subsystem, sometimes the filesystem,
> and the drives themselves (drives have no battery-backing thus their caches
> are purely read cache) will read-ahead several sectors, tracks, or even
> entire cylinders-- since the platters rotate under the heads once for
> either one sector, track, or a cylinder (only very high-end drives can
> activate more than one head at a time), might as well read it all. This is
> why read performance is typically so much faster than writes, but it is
> illusory-- actual reads and writes on the raw platters operate at the same
> speed.
>
Ahh, but my point was, since in this case, we are talking about a system 
thwch needs only to perform *reads* at the quoted spec, (it'sn not a 
read/write thing, it's just display of data) then it's *not* illusory, it's 
what the customer wants.  He's not going to complain if it can only write at 
150MB/sec, as long as it can read 300MB/sec...

George