Sometimes its the LEAST expected thing (that one this article does not cover).

Some time ago I had some really cheap SATA 2.5 SSD 256 GB in my laptop.

If generally worked well - system (FreeBSD) was responsive but ... when I deleted large file (like 1GB+ size) then the system almost FROZE ... until file is deleted.

After some investigation with Allan Jude (thanks again) we came to the conclusion that a single TRIM operation (for delete) take about 500ms (half a second) ...

By default ZFS on FreeBSD uses up to 64 TRIM operations PER SECOND (the vfs.zfs.vdev.trim_max_active setting) - so the SSD was literally DoS with TRIM operation and it crippled it to its knees.

After switching this option from 64 to 1 it solved all the problems and everything was smooth and fast again.

Details below.

    % grep -A 1 -i trim /etc/sysctl.conf
    # ZFS DELETE FUCKUP TRIM
    # vfs.zfs.vdev.trim_max_active: 64 -> 1
      vfs.zfs.vdev.trim_max_active=1

Hope that will help someone.

Regards,

vermaden