I run a similar but less sophisticated setup. About 18 TiB now, and I run it 16 hours a day. I let it sleep 8 hours per night so that it's well rested in the morning. I just do this on a cron because I'm not clever enough to SSH into a turned off (and unplugged!) machine.
4 drives: 42k hours (4.7 years), 27k hours (3 years), 15k hours (1.6 years), and the last drive I don't know because apparently it isn't SMART.
0 errors according to scrub process.
... but I guess I can't claim 0 HDD failures. There has been 1 or 2, but not for years now. Knock on wood. No data loss because of mirroring. I just can't lose 2 in a pair. (Never run RAID5 BTW, lost my whole rack doing that)
I use a wifi controlled powerpoint to power up and down a pair of raid1 backup drives.
A weekly cronjob on another (always on) machine does some simple tests (md5 checksums of "canary files" on a few machines on the network) then powers up and mounts the drives, runs an incremental backup, waits for it to finish, then unmounts and powers them back down. (There's also a double-check cronjob that runs 3 hours later that confirms they are powered down, and alerts me if they aren't. My incrementals rarely take more than an hour.)
4 drives: 42k hours (4.7 years), 27k hours (3 years), 15k hours (1.6 years), and the last drive I don't know because apparently it isn't SMART.
0 errors according to scrub process.
... but I guess I can't claim 0 HDD failures. There has been 1 or 2, but not for years now. Knock on wood. No data loss because of mirroring. I just can't lose 2 in a pair. (Never run RAID5 BTW, lost my whole rack doing that)