[Sussex] Hard drive question

[linux at oneandoneis2.org]

Hi all,

Google is giving me conflicting answers to this question, so I thought  
I'd try asking real people instead :o)

Hard drives with multiple platters & therefore multiple heads: When  
writing to the disk, is only one head active at a time, writing the  
whole file to one platter; or do all the heads write at once, with  
head one writing the first bit of the file, head two writing the  
second bit, and so on?

I was under the impression that only one head could write at any one  
time, and most sites seem to bear this out, but others swear blind  
that all platters are written to at once, and you can see how that  
would make for a speed increase. . .

Anybody know for sure?

Thanks

Dominic