We are planning to buy two servers which will going to host an SQL database(PostgreSQL). The second server will work as a live replication of the first database server (hot standby). The question I'm having is about the RAID level to chose for the servers.
Initially I was planning to use RAID 10 on both servers from performance point of view, but since we plan to store 20-30Tb of data during 5 years, RAID 10 gets a bit too expensive (especially since we have to buy two machines). And also I was thinking that the redundancy of RAID 10 is not really needed if we have replication anyway.
So now I'm considering having RAID 5 on each of the replicating servers. With this setup even if there is a failure of RAID 5 on one machine, accompanied by another failure during the rebuild I'll still have a working DB machine. My guess is that the system should be quite reliable this way. Do you think that's a reasonable decision ?
PS I don't really want to use RAID6, because of the write penalty of it.