No, I just tell snapraid that the data location is inside the PoolPart directory. For example, here's what my config looks like:
# Defines the data disks to use
# The name and mount point association is relevant for parity, do not change it
# WARNING: Adding here your boot C:\ disk is NOT a good idea!
# SnapRAID is better suited for files that rarely changes!
# Format: "data DISK_NAME DISK_MOUNT_POINT"
data d1 C:\mounts\HD_MODEL - HD_SN\PoolPart.99266457-9bf0-46da-8285-163b8b5fe9f8\
data d2 C:\mounts\HD_MODEL - HD_SN\PoolPart.9886f8bd-626d-4d6b-96c5-5f7633461856\
data d3 C:\mounts\HD_MODEL - HD_SN\PoolPart.9a0f11e0-8e4d-4022-a338-c814de2a4f87\
I chose to name my mounting points by the drive's model and then serial number so I can tell which is which. For my parity drive I changed the folder slightly to 'HD_MODEL - HD_SN - Parity' so, from a glance in that folder, I know which one is the parity drive.
https://www.snapraid.it/faq#howmanypar -- "As a rule of thumb you can stay with one parity disk (RAID5) with up to four data disks, and then using one parity disk for each group of seven data disks". I have three data drives and one parity so in theory I could add another data drive to the mix before adding an additional parity, but when I look at the parity file on the parity drive, it's already using 10TB of the 12TB so I think next time I add it'll be at least two drives so one of them can be an additional parity drive.
Also - apparently in older versions of snapraid you had to use your largest drive for parity so you may see that referenced on older posts. That's no longer the case though I don't understand it well enough to explain it further.
No, but I need to look into "safe" ways of testing this. I know a backup that hasn't been validated via restoration isn't a backup. I have 12TB drives so I'm imaging it will be very time consuming. Seems to me, based solely on forum posts I've read, most users trust snapraid's parity to cover them in a drive failure. Haven't verified so can't speak from experience, but that's also why I changed one folder to 2x duplication in drivepool.
Assuming this is all working like I think/hope it's working, I was really surprised at how easy it was to set all of this up and am super happy with drivepool and scanner. I also have clouddrive but haven't set that up yet.