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Sounds like you're a victim of WD selling Reds with Shingled Magnetic Recording (SMR). Quite a scandal a few years ago. SMR takes advantage of the fact read he

Sounds like you're a victim of WD selling Reds with Shingled Magnetic Recording (SMR). Quite a scandal a few years ago. SMR takes advantage of the fact read heads are often smaller than write heads, so it "shingles" the tracks to get better density. However, if you need to rewrite in between tracks that are full, you need to shuffle the data around so it can re-shingle the tracks. This means as your array gets full or even just fragmented, your drives can start to need to shuffle data all over the place to rewrite a random sector. This does hell to drives in an array, which a lot of controllers have no knowledge of this shingling behavior. Shingled drives are OK when you're just constantly writing a stream of data and not going to do a lot of rewriting of data in betweeen. Think security cameras and database backups and what not. They're complete hell if you're doing lots of random files that get a lot of modifications. https://www.servethehome.com/wd-red-smr-vs-cmr-tested-avoid-red-smr/ https://www.servethehome.com/wd-red-smr-vs-cmr-tested-avoid-...

kstrauser 3y ago
No, these were 100% CMR drives. I checked them very closely when the scandal broke and confirmed that mine were not shingled.
- vel0city 3y ago
  Huh, weird, because that's 100% the failure mode friends of mine who did have shingled drives experienced. Maybe your drives were shingled despite labeling suggesting otherwise, or maybe they had whatever potential different error you got without it being the SMR that killed the arrays in the end. Either way it made me never want to use WD for drives in arrays and not trust their labeling anymore. "WD Red" drives lost all meaning to me; who knows what they're doing inside.
  - kstrauser 3y ago
    > Maybe your drives were shingled despite labeling suggesting otherwise I'm not ruling that out. The whole debacle was so amazingly tonedeaf that I wouldn't be surprised if they did that behind the scenes. I wrote this at the time: https://honeypot.net/2020/04/15/staying-away-from.html https://honeypot.net/2020/04/15/staying-away-from.html

kstrauser 3y ago

No, these were 100% CMR drives. I checked them very closely when the scandal broke and confirmed that mine were not shingled.

vel0city 3y ago
Huh, weird, because that's 100% the failure mode friends of mine who did have shingled drives experienced. Maybe your drives were shingled despite labeling suggesting otherwise, or maybe they had whatever potential different error you got without it being the SMR that killed the arrays in the end. Either way it made me never want to use WD for drives in arrays and not trust their labeling anymore. "WD Red" drives lost all meaning to me; who knows what they're doing inside.
- kstrauser 3y ago
  > Maybe your drives were shingled despite labeling suggesting otherwise I'm not ruling that out. The whole debacle was so amazingly tonedeaf that I wouldn't be surprised if they did that behind the scenes. I wrote this at the time: https://honeypot.net/2020/04/15/staying-away-from.html https://honeypot.net/2020/04/15/staying-away-from.html