Firsthand knowledge and experience as a Seagate Partner discussing this
with several Seagate support technicians:
Most SCSI disc drives support spin down, but not all. For spin down to
work, there has to be several things.
1- the system must have software support to tell the drive when to spin
down (this may include or already be included in firmware on the SCSI drive
and/or controller).
2- the system has to properly see the drive. On many instances, I have seen
systems that never spin the drive down until powered off because the drive
is not seen as a proper drive (IE: using a drive larger than what can be
seen by SCSI BIOS, or as some know, using a drive as a 'dumb' replacement
for an older one that failed (see huge full-height Seagate SCSI drives for
older systems - Dave Woyciesjes knows about this as I personally know of
him implementing such a thing)).
3- there must be a trigger to cause the spin down (time out delay,
overheat, software command during diagnostics, etc.).
I hope that helps a bit. Oh, and almost forgot: I do know of some SCSI
drives that were never made with the spin down command (which I know is odd
since I believe it is part of the SCSI protocol, etc.) - Maxtor made a
small line with them and talking to Seagate, they had at least 2 of them
that lacked it. There are most likely a few from other brands, but those
are the ones I know of as is.
One last thing: for spin down, you don't need to have SCA. It can be just
about any SCSI interface or version from what I've been told. What you are
thinking about is spin down linked with hot swap, which is something else
(SCA only). This is because SCA has the power and SCSI all going through
one interface and circuit controlled. Other interfaces lack that and will
cause power fluctuations and SCSI errors that in many cases will lock a
system (a few older systems would sometimes forgive you and let the
disturbance slide without locking up).
Spin down was included in the specs because of power saving features. The
drive would still draw a little power and come back if an init or access
(read/write, etc.) command was passed. The spin down with SCA drives allows
with firmware and circuitry to make it ok to pull the drive with that small
amount of voltage left and automatically adjust for the change in number of
drives, etc.
Hope that helps. If need be, I can email you links to several references on
this topic, including white papers, tech specs for whatever drives you get
and software. Let me know how it goes.
-John Boffemmyer IV
At 07:10 AM 4/28/2004, you wrote:
Not sure if this it OT or not! Anyone know if all SCSI
disks support
spin-down under software control? Is it a SCSI-1 and above thing, SCSI-2
and above, or something which is only implemented by some manufacturers?
(Or maybe it only applies to modern disks with an SCA infterface even?)
I'm just thinking about putting some more drives in the home fileserver
- but it's noisy enough already, hence I'd like to be able to power-down
disks I'm not using except for when I need them. Possibly even hooking
into samba code to spin the disks down after x minutes of inactivity and
only spin them back up when a data request comes in...
As all my classic comp data will be on said drives I suppose that
sort-of makes it on topic :-)
cheers
Jules
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