On Tue, 19 Mar 2002 22:56:09 +0100, Vojtech Pavlik wrote:
>> > Not all of them safely, though. Many a drive will corrupt data if it
>> > receives a command when not spinned up. You need to issue a wake command
>> > first, which hdparm doesn't, it just leaves it to the kernel to issue a
>> > read command or whatever to wake the drive ...
>>
>> Is this common disk bug, or are they permitted to behave like that?
>
>This behavior is permitted by the specification, as far as I know -
Actually not. Have a look at page 36 of the current ATA6 specification.
>results of commands other than wakeup (and other pm commands) in sleep
>or suspend mode are undefined ...
If a disk is in power state PM1:idle or PM2:standby, each ATA command
which requires media access will result in a transition to power state
PM0:active as well. The driver should be prepared of a long command
execution time in this case (due to the spin up delay). This is why a
well implemented ATA driver should track the individual power states of
each attached unit to modulate its internal command timeout
accordingly.
The driver may issue a SET_FEATURES(spin up) command in anticipation of
a media access. A "forgiving" implementation might issue this command
at proper system state transitions as well .
If a disk has entered power state PM3:sleep, its interface is turned
off! You no longer can issue any command except for a DEVICE RESET to
this unit. A reset is required to initiate a state transition from
PM3:sleep to PM2:standby (there are no other state transitions).
Ciao,
Dani
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Daniela Engert, systems engineer at MEDAV GmbH
Gräfenberger Str. 34, 91080 Uttenreuth, Germany
Phone ++49-9131-583-348, Fax ++49-9131-583-11
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This archive was generated by hypermail 2b29 : Sat Mar 23 2002 - 22:00:21 EST