On 06/30/2011 10:21 AM, Karsten Römke wrote: > Hi Phil >> >> If your CPU has free cycles, I suggest you run raid6 instead of raid5+spare. >> >> Phil >> > I started the raid 6 array and get: > > Personalities : [raid0] [raid1] [raid10] [raid6] [raid5] [raid4] > md0 : active raid6 sde5[4] sdd5[3] sdc5[2] sdb2[1] sda3[0] > 13759296 blocks level 6, 64k chunk, algorithm 2 [5/5] [UUUUU] > [=================>...] resync = 87.4% (4013184/4586432) finish=0.4min speed=20180K/sec > > when I started the raid 5 array I get > > md0 : active raid5 sdd5[4] sde5[5](S) sdc5[2] sdb2[1] sda3[0] > 13759296 blocks level 5, 64k chunk, algorithm 2 [4/3] [UUU_] > [=>...................] recovery = 6.2% (286656/4586432) finish=0.9min speed=71664K/sec > > so I have to expect a three times less write speed - or is this calculation > to simple ? That's a bigger difference than I would have expected for resync, which works in full stripes. If you have a workload with many small random writes, this slowdown is quite possible. Is your CPU maxed out while writing to the raid6? Can you run some speed tests? dd streaming read or write in one window, with "iostat -xm 1" in another is a decent test of peak performance. bonnie++, dbench, and iozone are good for more generic workload simulation. Phil -- 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
