[1081] in linux-scsi channel archive
Re: why spin up...
daemon@ATHENA.MIT.EDU (Rik Faith)
Sat Dec 7 08:06:30 1996
To: linux-scsi@vger.rutgers.edu
From: faith@cs.unc.edu (Rik Faith)
Date: 7 Dec 1996 13:04:46 GMT
CC: faith@cs.unc.edu, A.Pour@sh.cvut.cz
In article <9A2B950153@notorola.sh.cvut.cz>, A.Pour@sh.cvut.cz (3-417.3 Ales Pour) writes:
|> I have BusLogic controller and 2 disks, jumpered to be spinned up
|> via START command. I have instructed the controller not to send
|> the command to the 2nd disk since I do not currently use it, I just
|> have it 'in'. Hovewer, linux spins up the second disk. It is not
|> a *problem*, I was just wondering why is linux doing that?
Your situation is rare (i.e., having a disk you don't want to use at all --
since Linux can mount many other foreign file systems, usually people want
their DOS, Win95, or OS/2 drives to be spun up).
The more common situation is that there are several SCSI disks in the
machine and you don't want them all spun up at power on (e.g., you want
them spun up sequentially to reduce the peak load on your power supply),
*AND* the controller doesn't have an option for sequential spin up (many
older controllers do not have this option). In this case, the OS must send
the START command if the drive is not already spun up.
You might argue that this could be done from user space after the kernel
has booted. I'd point out that there was historical necessity because of
problems reading partition tables after boot (this was several years ago).
Assuming this problem is fixed, you could work on patches to make the spin
up _optional_ and provide a utility to do the spin up in user space (which
might assume the generic SCSI driver (for /dev/sg*) which I might not want
to load -- so your patches should definitely be configurable so that
current behavior is preserved for those of us who like it). Another option
would be for you to spin down the drive from user space after the boot.
--
Rik Faith: faith@cs.unc.edu
"Unix and C are the ultimate computer viruses." -- Richard P. Gabriel
