On Thu, Jan 28, 2010 at 2:06 AM, Gabor Gombas <gombasg@xxxxxxxxx> wrote: > On Wed, Jan 27, 2010 at 10:16:12PM -0500, Yuehai Xu wrote: > >> md0 : active raid5 sdh1[7] sdg1[5] sdf1[4] sde1[3] sdd1[2] sdc1[1] sdb1[0] >> 631353600 blocks level 5, 64k chunk, algorithm 2 [7/6] [UUUUUU_] > [...] Do you mean there is something wrong when I setup my RAID5? The command I use to setup RAID5 is: mdadm --create /dev/md0 --level=5 --raid-devices=7 /dev/sdb1 /dev/sdc1 /dev/sdd1 /dev/sde1 /dev/sdf1 /dev/sdg1 /dev/sdh1 I don't think any of my drive fail because there is no "F" in my /proc/mdstat output >> Then I start IOZONE which starts 10 processes to do the sequential >> read(iozone -i 1). Each process read 640M file on each partition. The >> throughput of RAID0 is about 180M/s, while the throughput of RAID5 is >> just 43M/s. Why the performance between RAID0 and RAID5 is so >> different? > > You have a degraded RAID5 array with one drive missing, meaning the data > has to be recalculated from parity all the time. That obviously kills > performance. > > Gabor How do you know my RAID5 array has one drive missing? I tried to setup RAID5 with 5 disks, 3 disks, after each setup, recovery has always been done. However, if I format my md0 with such command: mkfs.ext3 -b 4096 -E stride=16 -E stripe-width=*** /dev/XXXX, the performance for RAID5 becomes usual, at about 200~300M/s. > > -- > --------------------------------------------------------- > MTA SZTAKI Computer and Automation Research Institute > Hungarian Academy of Sciences > --------------------------------------------------------- > -- 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
