Adding drives 512n, 512e and 4kn


Wow there are lots of things to think about for hard disks, the main one is the warranty and performance. Paying a little more for an enterprise drive makes some sense for a consumer because you are not BackBlaze. A failure takes time to resolve and with RAID arrays too many of them and you lose data. I normally get the Seagate Enterprise Capacity drives. These are 7200 rpm with a 5 year warranty and decent reviews on Newegg. They are not super fast, but for a home NAS, that doesn't matter that much.
However with drives today, you have a choice of sector sizes and there are some tradeoffs:

  • 512n. This means a native 512 byte sector. This was very efficient with a 40MB drive (yes those were a thing), but with a 4TB drive, it is inefficient because each sector needs its own error correction (so you are about 88%¬†efficient vs 97% for the larger 4kn drives.
  • 4kn. This means a native 4K sector, this has two advantages, first is the efficiency noted above also. With a 100 bit ECC, a single areal disk hit is less likely to take out all your error checking in a 50 bit ECC on 512n. The main issue is compatibility. With Synology for instance you cannot mix 512n/512e drives with 4kn drives. Most modern operating systems (Synology DSM 4 and higher) support them.
  • 512e. This means 512 emulated on a real 4K sector underneath. Thus, you get compatibility and efficiency with the sector format. However particularly for write, the disk controller has to read a 4K sector modify a 512 byte subsection and write it out, so it slows things down.

The net is that if you haven't been too worried about this, get the 512e drives. But if you are doing to have a dedicated array and then getting 4kn is the better long term choice until all

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