4 ms·

I just tested the mediocre enterprise nvme I have sitting on my desk (micron 7400 pro), it does over 30000 fsyncs per second (over a thunderbolt adapter to my l

• hawk_ 10mo ago
  If you tested this on macos, be careful. The fsync on it lies.
  • packetlost 10mo ago
    fsync on most OSes lie to some degree
  • Palomides 10mo ago
    nope, linux python script that writes a little data and calls os.fsync
    • ncruces 10mo ago
      What's a little data? In many situations, fsync flushes everything, including totally uncorrelated stuff that might be running on your system.
• saltcured 10mo ago
  Another complexity here besides syncs per second is the size of the requests and duration of this test, since so many products will have faster cache/buffer layers which can be exhausted. The effect is similar whether this is a "non-volatile RAM" area on a traditional RAID controller, intermediate write zones in a complex SSD controller, or some logging/journaling layer on another volume storage abstraction like ZFS. It is great as long as your actual workload fits, but misleading if a microbenchmark doesn't inform you of the knee in the curve where you exhaust the buffer and start observing the storage controller as it retires things from this buffer zone to the other long-term storage areas. There can also be far more variance in this state as it includes not just slower storage layers, but more bookkeeping or even garbage-collection functions.