Why is my HDD going back from standy?

My hard drives, connected to Ubuntu server are producing the following log every exactly 5 minutes.

Nov  1 14:10:50 localhost kernel: [ 1602.884936] ata2.00: hard resetting link
Nov  1 14:10:51 localhost kernel: [ 1603.226804] ata2.01: hard resetting link
Nov  1 14:10:52 localhost kernel: [ 1604.274533] ata2.00: SATA link up 3.0 Gbps (SStatus 123 SControl 300)
Nov  1 14:10:52 localhost kernel: [ 1604.274548] ata2.01: SATA link up 3.0 Gbps (SStatus 123 SControl 300)
Nov  1 14:10:52 localhost kernel: [ 1604.356669] ata2.00: configured for UDMA/133
Nov  1 14:10:52 localhost kernel: [ 1604.375247] ata2.01: configured for UDMA/133
Nov  1 14:10:52 localhost kernel: [ 1604.375265] ata2: EH complete


I don't think this is related to hard drive failure, because it happens for ALL hard drives connected and ONLY when I write

spindown_time = 12


in /etc/hdparm.conf. The reason I add this value is to put disks into standby mode after 60 seconds, which is happening after that period (checked with hdparm -C).

The first clue I thought that smartd was running and spinning the drive. However, I couldn't find it in ps -aux | grep smart.

Additionally, iostat does show that nobody accessed those drives, since Blk_read, Blk_wrtn remain unchanged. I also killed all processes that may be doing something with hdd(eg SAMBA). So I guess the problem is solely with hdparm...

I have no more clue where that 5 minute value hides.

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Just after this happens, try sudo find / -xdev -cmin -1 to see what files have been accessed in the last minute. That way you can be sure that the spinup is not caused by any file access. –  André Stannek Nov 1 '12 at 12:03
According to this no files are access on the subject hard drive. Any other ideas? –  Pablo Nov 1 '12 at 14:11
No, sorry. I'm interested in the answer myself now. –  André Stannek Nov 1 '12 at 15:25