https://blog.margrop.net/en/tag/btrfs/ Recent content in Btrfs on Margrop Blog Hugo en-US Thu, 09 Jul 2026 10:00:00 +0800 https://blog.margrop.net/en/post/smr-cmr-btrfs-disk-trap/ Thu, 09 Jul 2026 10:00:00 +0800 https://blog.margrop.net/en/post/smr-cmr-btrfs-disk-trap/ <blockquote> <p><strong>Short version</strong></p> <p>A hard drive is not just capacity divided by price. CMR behaves like normal lanes on a road: random rewrites are relatively predictable. SMR behaves like roof shingles: tracks overlap, density improves, but changing one small area may require rewriting a larger zone. The most dangerous detail is that SMR is not one thing. Some SMR drives hide the complexity in firmware. Some expose zone controls. Some are <strong>host-managed SMR</strong>, where the operating system and software stack must obey zone write rules. Recently, some very cheap large HDDs have been marketed as “Feiniu drives” or “Btrfs drives” on PDD-like listings. In many cases, the real risk is that these are host-managed SMR enterprise drives, not ordinary NAS drives.</p> <p>My buying rule is simple: <strong>no exact model, no purchase; no vendor datasheet, no purchase; Linux reports <code>host-managed</code>, normal users should walk away; if the seller talks about Btrfs or Feiniu but avoids the SMR type, walk away.</strong></p> </blockquote>