Gzip are very stable itself but it's just a compression and won't do backup alone.
And tar are just archiving software. It just doesn't do all the things that backup requires in modern environment alone.
You might want to check out some software especially designed for backups which will provide things like data consistency and other.
Sounds like this is Veeam.
I use RAID6 on all my nas devices when I am using a setup like yours. If it is a Windows Server I will use storage spaces with SSD tier and a capacity tier. RAID5 is unacceptable on big drives (still usable on SSD).
And yes, you need redundancy on redundancy. I take it a step further and replicate my backups out to AWS virtual tape ...
I posted this answer to an issue yesterday which will help (instructions duplicated below): https://github.com/influxdata/influxdb/issues/18882#issuecomment-663113088
You can manually edit the boltdb file to add those missing permissions to the token. Here's how:
Stop your influxd process
Upgrade to the latest influxd beta (currently beta-15).