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Best use of extra HDDs
(discuss.tchncs.de)
Hosting your own services. Preferably at home and on low-power or shared hardware.
Also check out:
Raid5 of three disks and keep the fourth as cold spare. That's 16TB instead of 24, but you're barely using your current 8, so a spare makes more sense.
Hmm I think RAID5 would be risky. If I have a 16TB array and then get a failure, resilvering would take long and that could bring a second disk down..