I have a Dell Poweredge r720xd in RAID10. I’ve had a couple of drives fail since I’ve bought it and was able to buy cheap replacements on ebay.
I had another drive fail recently and one of the spare ebay drives came up as “blocked”. It put me out a few days while I waited for a new one to arrive; also from ebay.
I’d like to avoid getting another dud drive. Are there any reputable resellers of these old drives so I can stock up on some spares?
This really depends on your exact setup and might not be true for hardware raid.
Generally speaking, I would look into replacing that ageing raid with something more modern like Btrfs or ZFS where you are significantly more flexible with the drives used.