On 5/14/05, Pawel Jakub Dawidek <[EMAIL PROTECTED]> wrote: > On Sat, May 14, 2005 at 01:22:05PM +0400, [EMAIL PROTECTED] wrote: > +> > +> Hardware: SATA RAID adapter with SiliconImage 3114 chip. 2 SATA HDD. > +> I did gmirror. > +> > +> Run test: > +> 3 parallel tasks "dd if=/dev/mirror/gm0 of=/dev/null bs=1m count=5000" > +> > +> gstat shows summary read speed from mirror about 30-40 mbyte/sec. > +> It is for all balance algorithms: load, round-robin, split > +> > +> While, one "dd if=/dev/ad4 of=/dev/null bs=1m count=5000" shows 50 > mbyte/sec > +> > +> 1. Why it occurs and how fix it ? > +> > +> 2. If in the test instead of three instancies of "dd if=/dev/mirror/gm0 > +> of=/dev/null bs=1m count=5000" run only one, > +> then read speed don`t exceeds read speed from one disk (dd > if=/dev/ad4 > +> of=/dev/null bs=1m count=5000) > +> a) This is gmirror feature ? > +> b) This is hardware feature (SiliconImage 3114 chip) ? > > This is the way RAID1 works. Try to imagine how disk's heads are moving - > there will be no speed-up in sequential reads, this is not RAID0. > > Mirror characteristics are: > - the same speed for sequential reads as for one disk; > - the same speed for sequential/random write as for one disk; > - double speed of one disk for random reads; by what test-suite I can test it ? and what balance algorithm is more proper for random reads ?
> > -- > Pawel Jakub Dawidek http://www.wheel.pl > [EMAIL PROTECTED] http://www.FreeBSD.org > FreeBSD committer Am I Evil? Yes, I Am! > > _______________________________________________ freebsd-stable@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-stable To unsubscribe, send any mail to "[EMAIL PROTECTED]"
