Linux software similar to primocache?

I’ve looked into bcache and a few other linux solutions, but none of them seem to work the way primocache does. What I want to do is this:

  1. Build a NAS
  2. Have 1-2 ultra-fast NVMe SSDs to accept data at as close to line rate (10Gb NICs) as possible, then destage that data to spinning HDD (because it’s still around 1/8th the cost of high-cap SSD) in the background.

Writes will be almost entirely sequential reads and writes. It will mostly hold movie and music files (NOT a plex server). I only need around 12TB of storage, so I won’t have enough spindles to get my speed that way. The reason I want the destaging is because I want to be able to move a 20GB file off my PC in a few minutes, rather than a few hours, and let that write out to disk in the background over time.

Every linux cache tiering software I find makes overall IO performance slower than drive speed. I see no good reason for this in such an ideal use case. There’s no reason a cache tier like this shouldn’t be able to accept data and write it to disk with, at most, a 5% speed penalty (1% with good optimization). Have I missed something, or does such software simply not exist for linux?

Have you looked at, or tried using dm-writecache with LVM?

Looks promising-ish. I could only find one benchmark that was kinda the same usecase as I have, but it was using random IO instead of sequential. I’ll have to tuck this away and actually test it later on when I have the hardware.

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