On 30/12/11 07:28, Michele Codutti wrote:

Hi all, I'm writing to this mailing list because I cannot figure out why I had some performance issues with my three WD20EARS (2TB Western Digital "Green" 4K/AF drive).
These drives has a (sequential) write throughput around 100MB/s. When I combine them in a RAID0 configuration the throughput is around 300 MB/s and in a RAID1 configuration they preserve a single drive performance of 100MB/s.
When I combine all three drives in a RAID5 configuration the (individual) performance falls around 40MB/s.
I get the same performance level when I do individual misaligned writes (ex: dd if=/dev/zero bs=6K of=/dev/sda).
The drives are not partitioned. I'm using the default chunk size (512K) and the default metadata superblock version (1.2).
I had not formatted the RAID or any single drive during my test i had directly used the raw devices.
I'm using a 11.10 ubuntu with 3.0.0 linux kernel and 3.1.4 mdadm.
The hardware is a HP microserver.

Just a thought, but do you have the "XP mode" jumper removed on all drives?

Regards,
Brad