rsync help the gramma

[betty]

I have an ext hdd that i copy my stuff to every few months. I think that 
i am copying everything all over again each time.
What I'd like to do is just copy files that have changed.
This is the command i have been using

stormy at stormy-desktop:~$ sudo rsync -azvH /home/stormy/ /media/october

please don't suggest that i use dd or whatever else there is because i 
am not good at trying new things. i think i'm doing a lot just to do the 
backup every few months.

any rsync suggestions greatly appreciated. if i am already using the 
correct command for just copying things that have changed, please let me 
know.

THANKS, Merry Christmas to all pluggers !

-- 
betty i.
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