Scott Long wrote: > The Areca controller likely doesn't buffer/cache for disks in JBOD mode, > as others in this thread have stated. Without buffering, simple disk > controllers will almost always be faster than accelerated raid > controllers because the accelerated controllers add more latency between > the host and the disk. A simple controller will directly funnel data > from the host to the disk as soon as it receives a command. An > accelerated controller, however, has a CPU and a mini-OS on it that has > to schedule the work coming from the host and handle its own tasks and > interrupts. This adds latency that quickly adds up under benchmarks. > Your numbers clearly demonstrate this.
That's nice to know. I'm not sure it tells us why the Non-Cached writes were about 8% faster though. The other thing about the "NoWriteCache" test I performed that I neglected to mention yesterday is that I actually panic'd the box (running out of memory). This was the first time I have had that happen with ZFS even though in previous testing (with cache enabled) I punished the box for a lot longer. Perhaps the ZFS caching took over where the disk caching left off? Could that explain why I did not see a negative difference in the numbers between Cache enabled and Cache disabled? One of the questions I wanted to answer for myself was just this: "Does a battery-backed cache on an Areca card protect me when I am in JBOD mode." If the Areca does not buffer/cache in JBOD mode then that means the answer is no. -D _______________________________________________ freebsd-hardware@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-hardware To unsubscribe, send any mail to "[EMAIL PROTECTED]"
