On Mon, 6 Mar 2006, Raz Ben-Jehuda(caro) wrote: > Neil Hello . > I have a performance question. > > I am using raid5 stripe size 1024K over 4 disks. > I am benchmarking it with an asynchronous tester. > This tester submits 100 IOs of size of 1024 K --> as the stripe size. > It reads raw io from the device, no file system is involved. > > I am making the following comparsion: > > 1. Reading 4 disks at the same time using 1 MB buffer in random manner. > 2. Reading 1 raid5 device using 1MB buffer in random manner. > > I am getting terrible results in scenario 2. if scenario 1 gives 120 MB/s from > 4 disks, the raid5 device gives 35 MB/s . > it is like i am reading a single disk , but by looking at iostat i can > see that all > disks are active but with low throughput. > > Any idea ? Is this reading the block device direct, or via a filesystem? If the latter, what filesystem? If ext2/3 have you tried mkfs with a stride option? See: http://www.tldp.org/HOWTO/Software-RAID-HOWTO-5.html#ss5.11 Gordon - 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
