On Wed, Mar 17, 2010 at 10:15:53AM -0500, Bob Friesenhahn wrote: > Clearly there are many more reads per second occuring on the zfs > filesystem than the ufs filesystem.
yes > Assuming that the application-level requests are really the same From the OP, the workload is a "find /". So, ZFS makes the disks busier.. but is it find'ing faster as a result, or doing more reads per found file? The ZFS io pipeline will be able to use the cpu concurrency of the T1000 better than UFS, even for a single-threaded find, and may just be issuing IO faster. Count the number of lines printed and divide by the time taken to compare whether the extra work being done is producing extra output or not. However, it might also be worthwhile to look for a better / more representative benchmark and compare further using that. Also, to be clear, could you clarify whether the "problem" you see that the numbers in iostat are larger, or that find runs slower, or that other processes are more impacted by find? > this suggests that the system does not have > enough RAM installed in order to cache the "working set". Possibly, yes. > Another issue > could be fileystem block size since zfs defaults the block size to 128K > but some applications (e.g. database) work better with 4K, 8K, or 16K > block size. Unlikely to be relevant to fs metadata for find. > Regardless, I suggest measuring the statistics with a 30 second interval > rather than 5 seconds since zfs is assured to do whatever it does within > 30 seconds. Relevant for write benchmarks more so than read. -- Dan.
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