The command "zpool scrub POOLNAME" will go through and check all the checksums for you, and, you should use either RAID1 or RAIDZ (similar to RAID5) so that if it does detect an error, then the other copy of the data can be used to correct it.

For snapshots - they only get made, if you make them (or setup an automated script that makes them). You can list the snapshots and see how much space each uses, as well.