ZFS dead on a 10.9 partition, not on another...

[nodarkthings]

... and after a while, the disk goes to sleep (be it mounted in SATA or in an external USB dock).

[ilovezfs]

Are you running the commands as root?

[nodarkthings]

Yes, I forgot to mention that: I'm doing everything either logged in as the Root user or using sudo.

[nodarkthings]

... and in /etc/zfs/ there's no zpool.cache, just the zed.d folder.

[ilovezfs]

OK, so one thing to bear in mind is that once it's cooked, it's cooked - meaning if any of the commands deadlock or hang, you will need to reboot to get back into a functional state. So if sudo zpool import tank hangs, a sudo zpool import in another window will hang, too. After a reboot, sudo zpool import might run fine if you haven't run sudo zpool import tank yet.

So from a clean boot, does sudo zpool import hang?

[nodarkthings]

Here I am, clean rebooted in an admin account (not the Root user), directly doing "sudo zpool import" (note that my pool drive is currently in the SATA bay) and...
Nothing.
I've checked the Console:
27/01/2015 14:07:53,313 sudo[721]: Bdha : TTY=ttys000 ; PWD=/Users/Bdha ; USER=root ; COMMAND=/usr/sbin/zpool import
27/01/2015 14:08:13,105 xpcd[275]: Info.plist does not contain an XPCService dictionary: /System/Library/Frameworks/Security.framework/XPCServices/SecurityAgent.xpc

I don't know if the xpcd line has something to do with it, just in case...
Now, the disk went to sleep and import is still hanged.

[ilovezfs]

While it's hung please run sudo spindump

[nodarkthings]

I rebooted, re "sudo zpool import" after quitting anything else and here is the spindump result.
Hmmm... another limitation from the site: "The file is too big, maximum allowed size is 256 KiB"

[nodarkthings]

spindump.txt.zip

(94.08 KiB) Downloaded 3814 times

Here it is compressed!

[ilovezfs]

Now please upgrade to rc5 and repeat the procedure.