No, those drives generally DON'T report 4k to the OS, even though they are. If they were, there'd be fewer problems. They lie and say 512b sectors for compatibility. My only suggestion would be to experiment with various partitioning, starting the first partition at 2048s or various points to see if you can find a placement that aligns the partitions properly. I'm sure there's an explanation, but I'm not in the mood to put on my thinking hat to figure it out at the moment. May also be worth using a different superblock version, as 1.2 is 4k from the start of the drives, which might be messing with alignment (although I would expect it on all arrays), worth trying the .9 which goes to the end of the device. On Thu, Dec 29, 2011 at 7:00 PM, Zdenek Kaspar <zkaspar82@xxxxxxxxx> wrote: > Dne 30.12.2011 0:28, Michele Codutti napsal(a): >> 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. >> >> Could you give me some advice? >> Thanks in advance. >> >> Michele-- >> 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 > > There must be some misalignment somewhere :( Do all drives really report > as 4K to the OS - physical_block_size, logical_block_size under > /sys/block/sdX/queue/ ?? > > NB: how does it perform with partitions starting at sector 2048 (check > all disks with fdisk -lu /dev/sdX). > > HTH, Z. > > -- > 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 -- 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
