Re: slow lvm

[mimo <mimo@restoel.net>]

Hi again and thanks to everyone who replied to this,


I had done some benchmarking on the individual partitions, md devices, and lvm device and it all seemed fine initially after aligning the partitions on 4k, I then rebuilt my raid 1 based lvm and it seemed fine for starters but now I'm back to the initial problems. In particular doing hard links (and deletes) in the xfs file system that lives on the lvm seems slower than before, especially when it hits the two WD20EARS drives (though I've created the xfs with a block size of 4096). As an additional complication there are two more Seagate drives in the lvm which perform as usual (but they are smaller, 1TB and 750GB respectively). I guess in a way it could be said that it's also helpful to have them as a comparison. The most notable difference in my graphs is the iowait on the WD disks which seems to be close to 100% quite a bit. 

I'm attaching my graphs sda and sdd are the WD drives, sdb, sdc are Seagate.

http://mimo.gn.apc.org/stuff/blue.html (sorry for the external link but the list doesn't allow attachments)

Any help very much appreciated.

Thanks,

mimo