--- Robert Watson <[EMAIL PROTECTED]> wrote: > On Sat, 30 Apr 2005, Arne WXrner wrote: > > 3. The man page geom(4) of R5.3 says "The GEOM framework > > provides an infrastructure in which "classes" can per- > > form transformations on disk I/O requests on their path > > from the upper kernel to the device drivers and back. > > > > Could it be, that geom slows something down (in some boxes the > > reading > > ops are very slow; in my box the writing ops are very slow)? > > [...] > against a further offset region of ad0. If they're against the > same bits of disk, the main difference here will be the > additional processing of the layers in the stack. A little > bit of math is required to figure out the offset, but dd > should be usable to figure out the incremental cost. > I used the following commands: 1. dd if=/dev/ad0s2a bs=16k count=10000 of=/dev/null 2. dd if=/dev/ad0 iseek=2100357 bs=16k count=10000 of=/dev/null (I think I did the math correctly; indeed the read speed of my ad0 varies between 45MB/sec (iseek=0) and 25MB/sec (in the end) with bs=128k). The results were nearly the same (both between 26MB/sec and 28MB/sec). Maybe I should have done it in single user mode.
My other hard disc ad1 (it is newer and bigger and faster and more furious) behaves better (but I can just try writing via the file system (ufs+s) and a final sync): The sync just needs .24sec of 18.28 seconds; the read and write speed is nearly the same (about 37MB/sec+/-1MB/sec). Is there anything else, that could help to find the reason for the difference between ad0's speed in R4.11 and R5.3? -Arne __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com _______________________________________________ freebsd-performance@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-performance To unsubscribe, send any mail to "[EMAIL PROTECTED]"
