https://blog.berezovskyi.dev/tags/synology/Recent content in Synology on berezovskyi notesHugoen-usSat, 16 May 2026 00:00:00 +0000https://blog.berezovskyi.dev/notes/seagate-hdd-4k-sector-synology/Sat, 16 May 2026 00:00:00 +0000https://blog.berezovskyi.dev/notes/seagate-hdd-4k-sector-synology/<h2 id="the-goal">The Goal</h2> <p>I was adding a new Seagate Exos X20 (ST20000NM007D, 20 TB) to my Synology DS1821+ running DSM 7.2.2. These drives ship from the factory in 512e mode - they physically use 4096-byte sectors but advertise 512-byte sectors for legacy OS compatibility. Since my NAS and DSM support native 4K sectors, I converted the drive to 4Kn (native 4K) before adding it to the storage pool.</p> <h2 id="why-native-4k">Why Native 4K?</h2> <p>512e is a compatibility shim. The drive&rsquo;s physical sectors are 4096 bytes, but when the OS writes a 512-byte block, the drive must read the entire 4096-byte physical sector that contains it, modify the relevant 512 bytes, and write the full sector back - a read-modify-write cycle on every write. Native 4K eliminates this: every OS write maps directly onto a physical sector.</p>