Seagate has introduced the Exos M series, a range of enterprise-grade mechanical hard drives available in 30TB and 32TB capacities. The two models, the 30TB CMR ST30000NM004K and the 32TB SMR ST32000NM003K, each offer a minimum of 3TB per disk and use a standard 3.
Serverpartdeals has done me well, drives often come new enough that they still have a decent amount of manufacturers warranty remaining (exos is 5yr) and depending on the drive you buy from them spd will rma a drive for 5 years from purchase (but not always, depends on the listing, read the fine print).
I have gotten 2 bad drives from them out of 18 over 5 years or so. Both bad drives were found almost immediately with basic maintenance steps prior to adding to the array (zeroing out the drives, badblocks) and both were rma’d by seagate within 3-5 days because they were still within the mfr warranty.
If you’re running a gigantic raid array like me (288tb and counting!) it would be wise to recognize that rotational hard drives are doomed and you need a robust backup solution that can handle gigantic amounts of data long term. I have a tape drive for that because I got it cheap at an electronics recycler sold as not working (thankfully it was an easy fix) but this is typically a super expensive route. If you only have like 20tb then you can look into stuff like cloud services, bluray, redundant hard drive, etc. or do like I did in the beginning and just accept that your pirated anime collection might go poof one day lol
What kind of tape drive are you using? My array isn’t as large as yours (120tb physical), but it’s big enough that my only real options for backup are tape or a whole secondary array for just backup.
Based on what I’ve seen, my options are a prohibitively large number tapes with an older LTO standard or prohibitively expensive tapes with a newer LTO standard.
My current backup strategy consists of automated backups to Backblaze B2 for the really important stuff like personal documents or projects and hoping my ZFS array doesn’t fail for everything else.