LVM on two disks - spin down?

[b-misc]

Hi all,

If I have a LVM which uses two partitions on two different disks and at least 
one of its subvolumes is always in use, can the second disk spin down?

An example showing what I mean:
 _ _ _ _ _ _ _ _      _ _ _ _ _ _ _ _
|/dev/sda1      |    |/dev/sdb1      |
|_ _ _ _ _ _ _ _|    |_ _ _ _ _ _ _ _|


lvmGrp  =  /dev/sda1 + /dev/sdb1
 _ _ _ _   _ _ _       _ _ _ _ _ _
|lvm1   | |lvm2 |    |lvm3       |
|_ _ _ _| |_ _ _|    |_ _ _ _ _ _|

So since sdb is new, if I add lvm3 it will be on sdb1 and not sda1, correct?; 
if I don't mount lvm3 automatically, can sdb spin down although lvm1 and lvm2 
are used?

The reason for this setup is the possibility to extend e.g. lvm2 later with 
space on sdb1 if it is really required without any re-formatting. (Of course I 
will loose the spin down then, but for the time being I'd take care of my new 
disk.)

Thanks in advance...

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