On Feb 7, 2011, at 1:10 PM, Yi Zhang wrote: > > This is actually what I did for 2.a) in my original post. My concern > there is that ZFS' internal write buffering makes it hard to get a > grip on my application's behavior. I want to present my application's > "raw" I/O performance without too much outside factors... UFS plus > directio gives me exactly (or close to) that but ZFS doesn't...
In the bad old days when processors only had one memory controller, one could make an argument that not copying was an important optimization. Today, with the fast memory controllers (plural) we have, memory copies don't hurt very much. Other factors will dominate. Of course, with dtrace it should be relatively easy to measure the copy. > Of course, in the final deployment, it would be great to be able to > take advantage of ZFS' advanced features such as I/O optimization. Nice save :-) otherwise we wonder why you don't just use raw disk if you are so concerned about memory copies :-) -- richard
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