Which backup method?

So I see that the file backup method is using a proprietary binary called fvbackup.  Anyone know if there is any information about what this binary does in terms of backup verification, incremental policies, etc.?  I would presume it's doing all the same things that rsync does but I should not presume anything.  Just want to understand if this is still the best solution when backing up to local volume if it would be better in any way to use rsync, even to localhost.  I have another old readynas here I could also setup as a dedicated backup server, but its ultra 2 plus with only 1gb, probably I'd want to upgrade the ram to 2gb and upgrade it to OS6, etc..which might be worth the $20 to get that ram and have rsync backup to separate device, which is actually a slightly more safe 321 backup strategy..  So I am considering that, but on the other hand, I perceive that in the next couple years I will move to an entirely new NAS system, probably truenas but who knows...so..I am more keen to move on from my old readynas devices and just looking for simple interim solution, which I think its probably using USB drive plugged into my 524X and using the file backup method....simple...so long as the fvbackup program is doing everything I would expect it to be doing.

So the questions are 

1. does it create temporary snapshot to backup from?  I am guessing yes, but want confirmation
2. does it do incremental backups, and if so is it just based on filesystem timestamps or what is protocol?
3. does it do any verification of the backup itself, such as rsync -v does?  Any checksum checking?
4. is there anything more efficient about it compared to rsync?  
5. anything else to point out would be appreciated.

I think I have decided that readyDR is out at this time.  It would have been great back in the day with readyVault and all that.. powerful system, perhaps more efficient transfers...but its also quite proprietary and what if my readynas system goes totally down for some reason...I would not be able restore anything without obtaining a new readynas that support readyDR...so I am just leaving that out of the discussion now.