On Tue, Aug 22, 2006 at 06:15:08AM -0700, Tony Galway wrote: > A question (well lets make it 3 really) ? Is vdbench a useful tool > when testing file system performance of a ZFS file system? Secondly - > is ZFS write performance really much worse than UFS or VxFS? and Third > - what is a good benchmarking tool to test ZFS vs UFS vs VxFS? ... > sd=ZFS,lun=/pool/TESTFILE,size=10g,threads=8 > wd=ETL,sd=ZFS,rdpct=0, seekpct=80 > rd=ETL,wd=ETL,iorate=max,elapsed=1800,interval=5,forxfersize=(1k,4k,8k,32k)
ZFS write performance should be much better than UFS or VxFS. What exactly is the write workload? It sounds like it is doing effectively random writes of various (1k,4k,8k,32k) record sizes. As these record sizes are all smaller than ZFS's default block size (128k), they will all require ZFS to read in the 128k block. Whereas UFS (on x86) uses a 4k block size by default so the 4k, 8k, and 32k record size writes will not require any reads, only the 1k records will require UFS to read the block in from disk. When doing record-structured access (eg. databases), it is recommended that you do 'zfs set recordsize=XXX' to set ZFS's block size to match your application's record size. In this case perhaps you should set it to 4k to match UFS. > I am seeing large periods of time where is no reported activity, and > if I am looking at zfs iostat I do see consistent writing however How are you measuring this "reported activity"? If your application is trying to write faster than the storage can keep up with, then it will have to be throttled. So if you are measuring this at the application or syscall level, then this is the expected behavior and does not indicate a performance problem in and of itself. --matt _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
