Q4. If we need to avoid damage from SDC, would it be costly to purchase or even build such Btrfs/ZFS NAS for home user?
The answer is NO, those server board & ecc ram are bearable for home user now. ~HK$2000 budget: 4 bay HP microserver gen8 & 4GB ECC ram (incl. shipping fee) ~HK$2000 budget: 6+ bay HP ML10 v2 & 4GB ECC ram (incl. shipping fee)
with extra HK$500: DDR3 1600MHz 8GB ECC RAM (max. 16gb for gen8 & 32gb for ml10 v2) from here
you can even upgrade to Xeon CPU later.
%---% It's not expensive to get server grade hardware for building your Raid1 Btrfs or Raidz1-3 ZFS NAS!
Q5. For the case of ZFS system, how many hard disk is required for RaidZ1, RaidZ2 & RaidZ3?
The answer is at least 3 same size hard drives. http://wintelguy.com/raidcalc.pl http://biduleohm.free.fr/zfsraidsarc/
RaidZ1(single parity) - min. 3 HDD = 2 usable + 1 can be failed at the same time. (4:3+1, 5:4+1, 6:5+1 ... etc)
RaidZ2(double parity) - min. 4 HDD = 2 usable + 2 can be failed at the same time. (5:3+2, 6:4+2, 7:5+2 ... etc)
RaidZ3(triple parity) - min. 5 HDD = 2 usable + 3 can be failed at the same time. (6:3+3, 7:4+3, 8:5+3 ... etc)
More HDD more Storage in each raid. http://jrs-s.net/2015/02/06/zfs- ... or-vdevs-not-raidz/
%---% For affordable home used server with general 6 bay:
better Reliability & Performance: For 6 HDD, Stripped RaidZ1 = only 2 usable + 1 can be failed at the same time in each Raid group (total 2)
More Storage: For 6 HDD, RaidZ2 = 4 usable + 2 can be failed at the same time in each Raid group. https://icesquare.com/wordpress/ ... -raidz3-vs-striped/