it reads raw. no filesystem whatsover. On 3/6/06, Gordon Henderson <[EMAIL PROTECTED]> wrote: > 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 >
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