https://docs.fortinet.com/document/fortianalyzer/6.2.5/administration-guide/420493/modes
https://docs.fortinet.com/document/fortianalyzer/6.2.5/administration-guide/621804/log-forwarding

RAID 1 provides fault tolerance through disk mirroring.
RAID 5 provides fault tolerance by using distributed parity across multiple disks.
RAID 6+0 combines striping with double parity, offering enhanced fault tolerance.
RAID 0 and RAID 0+0 do not provide any fault tolerance, as they focus on performance through data striping but offer no redundancy.

Reference: https://docs.fortinet.com/document/fortianalyzer/7.0.1/administration-guide/651442/fetcher- management Using FortiAnalyzer, you can enable log fetching. This allows FortiAnalyzer to fetch the archived logs of specified devices from another FortiAnalyzer, which you can then run queries or reports on for forensic analysis.
The FortiAnalyzer device that fetches logs operates as the fetch client, and the other FortiAnalyzer device that sends logs operates as the fetch server. Log fetching can happen only between two FortiAnalyzer devices, and both of them must be running the same firmware version. A FortiAnalyzer device can perform either the fetch server or client role, and it can perform two roles at the same time with different FortiAnalyzer devices at the other end.
FortiAnalyzer_7.0_Study_Guide-Online pag. 168