Comment 13 for bug 568120

I've also tried the laptop mode tools. Somehow this seemed to spindown the disks while MD had not flushed its writes to the disks, or it did something else so I ended up with 4 disks and no array. After some crash recovery I managed to get a degraded array back with 3 out of the 4 disks.
I got the 4th disk added to the array, and after some hours array was rebuild. It kinda takes the fun out of testing with live data on the disks. There's a bit over 1 Tbyte of data on the array, and backup / restoring is kinda time consuming.

@pjotr12345, I did not get my disks to spindown from commandline with hdparm -Y /dev/sd[a-d]. I did see "issueing sleep command" for all four disks, but straight after a hdparm -C /dev/sd[a-d] all disks show idle/running instead of standby.