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SubjectRe: scsi disks spin down?
Ivan Popov <pin@math.chalmers.se> wrote:
>
> Just wondering if there is any technical reason for scsi disk driver
> not being able to spin disks down on idle timeout, like ide does.

The IDE spin-down is performed by the IDE disk *hardware*, not the
driver. The IDE drive simply notices that it has not heard any commands
in XX seconds, so it spins down. If it receives a later command, it
spins up, then processes the command.

With SCSI, the driver must figure out that it hasn't sent any commands
to a device lately, and then send a command to spin-down the drive. The
drive will then report errors ("not ready") if any further commands are
sent, so the driver must know that it has spun-down a drive, and spin it
back up if more commands need to be sent.

Thus, spin-up/down code complicates the driver for a rather small gain.

--
fox@dallas.net (Fuzzy Fox) || "Nothing takes the taste out of peanut
sometimes known as David DeSimone || butter quite like unrequited love."
http://www.dallas.net/~fox/ || -- Charlie Brown

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