HDD spinup when in sleep mode, strange behaviour

[komodo <komodo@uvt.cz>]

Hi

I have noticed some strange behavioir on my system. After some upgrade, i 
don't know exactly when, maybe one or two weeks ago, my drive which is in 
sleep state wakes up everytime when some process access it.
To be clear, here is my config.

I have two HDDs, one is main disk where is the system, data and so on, and 
second where is backup. Second disk is put in the sleep mode right after 
system start with hdparm

hdparm. conf

/dev/sdb {
    spindown_time = 10
}

Everything works fine, but now, every 30min i hear that disk is spined up, and 
after ten seconds is spinned down. So i thought that the problem is in the 
smartd, which check disks every 30min's, but it isn't, becase even if i run

hdparm -C /dev/sdb

the drive is spinned up again. 

And it's annoying, because before upgrade it was ok, and disk was spin up only 
after some access, fdisk, or mount or so.

Can someone tell me where the problem can be ? Or test it ?

A can't find any bug report about this behaviour. And i don't want fill new 
bugreport if i'm not sure that it's really bug and not some 
missconfiguration.

Thanks

Martin