Ah! I found out!
At http://www.kernel.org/doc/Documentat...parameters.txt, it states,
So, the tricky part is finding out which port X and device Y (dmesg ataX.YY) is which controller and drive. I think - that notation matches PORT[.DEVICE], but there's also the W:X:Y:Z notation. I'm guessing ataX.YY
libata.force= [LIBATA] Force configurations. The format is comma
separated list of "[ID:]VAL" where ID is
PORT[.DEVICE]. PORT and DEVICE are decimal numbers
matching port, link or device. Basically, it matches
the ATA ID string printed on console by libata. If
the whole ID part is omitted, the last PORT and DEVICE
values are used. If ID hasn't been specified yet, the
configuration applies to all ports, links and devices.
If only DEVICE is omitted, the parameter applies to
the port and all links and devices behind it. DEVICE
number of 0 either selects the first device or the
first fan-out link behind PMP device. It does not
select the host link. DEVICE number of 15 selects the
host link and device attached to it.
The VAL specifies the configuration to force. As long
as there's no ambiguity shortcut notation is allowed.
For example, both 1.5 and 1.5G would work for 1.5Gbps.
The following configurations can be forced.
* Cable type: 40c, 80c, short40c, unk, ign or sata.
Any ID with matching PORT is used.
* SATA link speed limit: 1.5Gbps or 3.0Gbps.
* Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
udma[/][16,25,33,44,66,100,133] notation is also
* [no]ncq: Turn on or off NCQ.
* nohrst, nosrst, norst: suppress hard, soft
and both resets.
* dump_id: dump IDENTIFY data.
If there are multiple matching configurations changing
the same attribute, the last one is used.
Luckily, I just did this mapping manually last week (trying to identify a drive that was throwing spasms and resetting a host controller), so I have an exhaustive list already I couldn't find anywhere that the mappings from sdX to ataX.Y or W:X:Y:Z where listed, so I ended up simply yanking out SATA cables and watching which ataX.YY messages appeared in /var/log/messages
So, in my setup, it seems I need to do
Gonna have to try that out as soon as my ZFS scrub finishes, and report back Awesome! Hope this helps someone else