Hi,as for alignment, please also check md metadata format version (-e switch of mdadm). The version that ensures alignment is 1.0, which places the metadata information to the back of the drive. I am not an expert to LVM but I would suspect that there might be similar problems/options to check.
I would first verify physical sector size of the drives you use. Please have a look at the utility at http://www.farm.particle.cz/blksztester.tar.gz. It randomly directly writes e.g. 4K blocks to a block device at choosen alignment. Run it with no arguments to get some help in English (README is in Czech :). If you get similar speeds for 4k-align and 4k-misalign writes, the disk use 512b physical sector size. The difference should be around 300% in case of 4K sectors. You may try to google for sector size according to product number, but I have seen cases where official vendor websites were wrong. Please note that you shold not connect the drive under test through RAID controller with its own logic and/or cache, which may skew the results, but rather to a stupid motherboard.
I had several headaches with 4k-block drives in the past as well... Cheers Jiri Horky On 03/12/2012 02:58 PM, Erwan MAS wrote:
On Mon, Mar 12, 2012 at 02:02:36PM +0100, Caspar Smit wrote:Hi Erwan, I do not use partitions on the drives so the whole disk /dev/sdb is used as md component device, i was in the understanding that if not using partitions the alignment is correct or am i wrong?For me it's correct .
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