tankist02 wrote:In my experience ZFS is fast right after reboot. But then the longer I work in the system the slower it gets. I suspect ZFS slows down when internal caches are filled up. I don't see this effect with UFS.
That's a rather strange behavior, a filled cache should improve performance, that is what cache is for. However ZFS is a complex subsystem and there could be something else going on.
I have also some suspect about some "memory management", because I had experienced myself bad performance in some cases; specifically I had bad performance while using 512byte blocks (both UFS and ZFS), and good performance when using 4K alignment and block size (again both UFS and ZFS). The strange thing in my case is that the disk was really a 512 byte sector (Hitachi 500 GB).
Unfortunately there are too many variables into the game and I was not able to track down exactly what is causing this performance difference, but I know it was real.