before the 621 sbf was released i thought i had bricked my phone because i was experimenting with cm9, when the phone restarted and i wound up stuck at the M logo ... long story short, i flashed the 602 sbf and that's how i bricked it. verizon sent me a new phone because it was still under warranty. the phone came with 605. i rooted it, then installed OTA rootkeeper. then i installed 621 and my root was preserved. but i went back to cm7.1, because i found some bugs with 621 (i.e., it wasn't letting me set up my alarms properly). so this new phone started out with 605, then i went to 621, now i am running cm7.1 from a backup i had made on my sd card from my previous phone. so far it's running ok, but i want to know that i can go back to 621 safely .... so the history of this phone so far is: started with 605 rooted (oneclick) ota rootkeeper saved root updated to 621 backed up 621 in bootstrap restored cm7.1 in bootstrap i want to know more about how system and data are organized/structured on the phone. so when i am doing backups/restores from clockworkmod, is that completely wiping memory of any trace of software to start fresh, or are some remnants of the old filesystem still in tact/not erased ?