On Mon, Mar 18, 2013 at 12:30:50AM +0100, Rainer Fügenstein wrote:

hi,

for some reasons I need to keep power consumption at startup as low as
possible. since the server is booting from SSD, it is possible to send
a "start unit" (or similar) command to all SATA drives early in the
init process.

as far as I've searchengined, the drives and the SATA controller need
to support this feature. but my assumption is that when the drives are
not needed at startup (since they would be started by the OS), the
controller won't need to support "start unit".  what is your
experience on this matter? 

drives in question are WD Green 3TB drives (WDC WD30EZRX-00DC0B0), the
controllers at hand are a promise SATA 300 TX4 (don't laugh ;-) ) and
a supermicro AOC-SAT2-MV8.

Hi Rainer,

I'm facing a similar issue.

That's what I got so far...

Many HDDs, but it seems not all, support the so
called Staggered Spin Up, this means they are in
sleep mode, when powered up.
A SATA bus scan will wake them up.

The Linux AHCI driver performs, per default, but
it could be changed by parameter, a serial bus
scan. This means it will wake up the HDDs one after
the other sequentially and not alltogether.
At least, this is what I understood, but I did not
tested it personally, I just trust the information
I found around.
Check "Linux AHCI SSS" with some search engine and
some patience.

Other drivers I do not know.

If you boot from SSD and you program the HDDs to
stay sleepy (jumper, firmware or cable select,
more info at https://en.wikipedia.org/wiki/Spin-up
and referenced links) it *should* work.

Hope this helps,

bye,

pg

tnx.

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piergiorgio
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