On Sun, 2008-09-21 at 12:53 -0700, John R Pierce wrote: > Kay Diederichs wrote: > > BTW, there is - even with current kernels - no speed gain in using > > RAID1 - see http://kernelnewbies.org/KernelProjects/Raid1ReadBalancing . > > except, thats wrong. I unwrapped a recent kernel source tarball from > kernel.org and found... > > static struct mirror *choose_mirror(struct mirror_set *ms, sector_t sector) > { > struct mirror *m = get_default_mirror(ms); > > do { > if (likely(!atomic_read(&m->error_count))) > return m; > > if (m-- == ms->mirror) > m += ms->nr_mirrors; > } while (m != get_default_mirror(ms)); > > return NULL; > } > > > so it appears its a round robin ... > _______________________________________________ This makes sense. I'm pretty sure that tests that I've run in the past using bonnie++ or iozone showed faster reads with raid1 than with a single drive. I would think that if the drives are on seperate controllers (and depending upon the performance/capacity of the drives and controllers), there could be notable improvements. Nataraj