On Thu, May 30, 2019 at 06:01:29PM +0200, Reindl Harald wrote: > > > Am 30.05.19 um 17:58 schrieb keld@xxxxxxxxxx: > > so you will not get performance gains if you read one file sequentially in raid10,near > > nor md raid1, reading 2 different files concurrently theoretcally should give the same > > speed in md raid1 an mdraid10,near - but I think raid10,near only reads from one device. > > so it is a driver issue. > > but why? > > you have two simple mirrors, read from both disks, one half from mirror1 > and the second from mirror2 if you have one file and you read every other block from each mirror then you loose a lot of reading capacity. say you read block 0 and 2 from mirror1 and block 1 and 3 from mirror2, then after reading block 0 from mirror1 you have to skip block 1 on mirror1 to read block 2, given that the disk is rotating anyway to advance to block 2. you could just as well read block 1 from mirror1 so all your reading frem mirror2 is unnessecary, and you could use mirror2 for other things. it is a matter o the disk drivers strategy. keld
