Tim Moore <linux-raid@xxxxxxxxxx> wrote: > Andy Smith wrote: >> Are reads from a 2 device RAID-1 twice as fast as from a single > md14 : active raid0 sdb13[1] sda13[0] > md13 : active raid1 sdb12[1] sda12[0] > > /dev/md14: > Timing buffered disk reads: 272 MB in 3.01 seconds = 90.37 MB/sec > /dev/md13: > Timing buffered disk reads: 164 MB in 3.00 seconds = 54.67 MB/sec And this is exactly the strange thing which I'm also experiencing and which was asked a lot of times on this list already, IIRC. Why is the single-stream read-performance of a RAID1 so much worse than the read-performance of a RAID0. A RAID1 should easily be able to gain (or perhaps even advance, since it's not bound to chunk borders) the read-performance of a RAID0. As far as I can see, RAID1 only does that in case of lots of parallel scheduled read-requests. Would it probably make sense to split one single read over all mirrors that are currently idle? regards Mario -- I've never been certain whether the moral of the Icarus story should only be, as is generally accepted, "Don't try to fly too high," or whether it might also be thought of as, "Forget the wax and feathers and do a better job on the wings." -- Stanley Kubrick - To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
