On Sun, Feb 15, 2004 at 03:35:32PM -0500, Mark Hahn wrote: > > > The you don't get as good performance because hdc1 is slow enough to > > > really drag it down. > > right. > > > I would have thought the disks would have worked towards gaining > > performance enhancements in some cumulative way, is that not so, in theory? > > raid0 stripes IO across devices, so more devices help, in general. > but suppose your config stores 1k per disk. a 3k write would > touch all three disks. when would that write complete? according > to your numbers, hdc1 takes much longer than the other two. > that means that a large upper-level IO request (all three disks) > will complete at about 3x16 MB/s (ignoring overhead, etc). So max thruput in sequential read would never be faster than the slowest disk times the total number of drives. Sounds right there, then 3 * 16 is 48, close to the observed value of 45. > > > You probably can't get 100mb/s with the two because that would be pretty > > > efficient, and there's probably more overhead than that. > > 100 MB/s is a pretty agressive goal for a duron: the speed of the CPU and > memory bandwidth *DO* have a significant effect on how well raid0 scales, > and where it tops out. hdparm -t is also quite cpu-inefficient, as > benchmarks go. Why should the duron CPU speed be a problem? Or the RAM? > > > Shouldn't the 80gb drive be going faster than 16mb/s though? Have you > > > checked hdparm to make sure dma and all the goodies are turned on for > > > it? > > 16 MB/s is a clear config or measurement mistake. 16 MB/s is the speed of > disks from 5+ years ago, and >= 80G didn't exist back then. yeah, something is wrong there. I observed a going of about 40 MB/s a couple of days ago on the same disk. keld - To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
