Re: Camcontrol question related to Seagate disks

On 2023-06-06, Karl Denninger <karl@denninger.net> wrote:
> Certain "newer" Seagate drives have an EPC profile that doesn't interact 
> as expected with the camcontrol "standard" way to tell spinning disks to 
> go into an idle state.
>
> Specifically those that support this: 
> https://www.seagate.com/files/docs/pdf/en-GB/whitepaper/tp608-powerchoice-tech-provides-gb.pdf

"This" whole lengthy babble sounds just like EPC.

> The usual has been "camcontrol idle da{x} -t 600" has typically resulted 
> in a 10 minute timeout, after which it goes into low power

I entertain quite a zoo of disks of various brands and ages, and my
impression is, about a third of them might behave as "typically"
expected in that regard. And practically every model behaves
different, some of them in an obscure and unexpected way.

Sadly I don't have actual SAS devices available (and it doesn't get
clear to me if Your's is SAS or SATA).
With SATA You can send low-level commands to the disk via
'camcontrol cmd' - *IF* you manage to figure out what these commands
should read.

> (sometimes 
> you want "standby" rather than "idle" depending on the recovery time and 
> power mode you're after and the specifics of the drive in question.)

And which one would You want?

Short abstract of the crap:
 - deskstar/ultrastar older models may have a two-level timer variable
   with separate values for idle and stop.
 - WD (whatever rainbow) may have the timer value hidden behind a "vendor
   specific" gate, as described on truenas ("hacking green and red...").
 - ultrastar (newer) may have EPC, but the timer values have only
   vague realtime resemblance.
 . seagate (consumer) may be configured to kill themselves with an
   incredible amount of almost immediate parkings.
 - ...

I for my part got tired of the whole stuff, and there is a little tool
in ports sysutils/gstopd, that can be easily expanded to handle SATA,
and then the machine (and not the disk) will control when the disk is
to stop. (ask me for patch)

> The reason is that /it appears //these drives, on power-up, do not 
> enable the timers /until and unless you send a SSU "START" with the 
> correct power conditioning bits. Specifically, the power conditioning 
> value of "7h" has to be specified.  If its not then the EPC timers are 
> present but, it appears, they are not used.

If You can figure out how this command should actually look like
byte-wise, you can probably send them.

> Does anyone know the proper camcontrol command to do this?  The "start" 
> command sent when the system spins up does not appear to do so.  If I 
> send an "idle" or "standby" to the drive with a timeout it takes
> effect

That stays unclear to me. "start" is SCSI, "idle" and "standby" is
SATA.

> immediately but any access to it spins it up (as expected) and it does 
> not re-enter the lower-power mode on the timer, implying that the SSU 
> command did not enable the timers, and thus they remain inactive even 
> though they ARE set and camcontrol does report them.

Hm, what is SSU? Staggered Spin-Up? I'm trying to configure delayed
spin-up with this one on plain SATA:
# camcontrol cmd /dev/ada2 -a "EF 06 00 00 00 00 00 00 00 00 00 00"
but that doesn't really work, because the device driver has it's own
ideas about when to taste the device...

No, wait...

> To allow unlimited flexibility in controlling the drive’s
> PowerChoice technology feature, the Start/Stop Unit (SSU) SCSI
> command can be used.

Hm... so this would be the *SCSI* command 0x1B... then this one should
work (here is the 'STOP' incantation; replace with Your proper bit values
according to that seagate paper):
# /sbin/camcontrol cmd /dev/xxx -c "1B 01 00 00 00 00"

HTH
PMc