Artem Kuchin wrote: >>> Artem Kuchin wrote: >>> Hmm. what kind of HDD, RAID or whatever are you using? >>> My raid pretty much sucks. It is build it on the intel motherboard >>> LSI Megaraid. But i still get 81Mb/sec when doing >>> dd if=/dev/ar0 of=/dev/null bs=1M >>> >>> How much do you get on this? >> >> geom_mirror on 2 desktop SATA drives, but the results of dd are >> pretty low: >> >> # dd if=/dev/mirror/data of=/dev/null bs=1m count=1000 >> 1000+0 records in >> 1000+0 records out >> 1048576000 bytes transferred in 17.817686 secs (58850290 bytes/sec) >> >> As you can see, results with a single drive are better: >> >> # dd if=/dev/ad4 of=/dev/null bs=1m count=1000 >> 1000+0 records in >> 1000+0 records out >> 1048576000 bytes transferred in 16.219518 secs (64649023 bytes/sec) > > How is it possible that you get 2x file copy perfomance ? What's the > matter?!
If you use dd on the raw device (meaning no UFS/VFS) there is no read-ahead. This means that the following DD-command will give lower STR read than the second: no read-ahead: dd if=/dev/mirror/data of=/dev/null bs=1m count=1000 read-ahead and multiple I/O queue depth: dd if=/mounted/mirror/volume of=/dev/null bs=1m count=1000 You can test read STR best with bonnie (see /usr/ports/benchmarks/bonnie); or just with DD on a mounted volume. You should mount with -o noatime to avoid useless writes during reading, or use soft updates to prevent meta data from taking it's toll on I/O performance. - Veronica _______________________________________________ freebsd-stable@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-stable To unsubscribe, send any mail to "[EMAIL PROTECTED]"
