On Sun, Jun 10, 2007 at 01:56:20AM +0200, Peter Rabbitson wrote: > Hi, > > This question might be better suited for the lvm mailing list, but > raid10 being rather new, I decided to ask here first. Feel free to > direct me elsewhere. > > I want to use lvm on top of a raid10 array, as I need the snapshot > capability for backup purposes. The tuning and creation of the array > went fine, I am getting the read performance I am looking for. However > as soon as I create a VG using the array as the only PV, the raw read > performance drops to the ground. I suspect it has to do with some minima > l tuning of LVM parameters, but I am at a loss on what to tweak (and > Google is certainly evil to me today). Below I am including my > configuration and test results, please let me know if you spot anything > wrong, or have any suggestions. > [snip] > > > root@Arzamas:~# dd if=/dev/md1 of=/dev/null bs=512 count=4000000 > 4000000+0 records in > 4000000+0 records out > 2048000000 bytes (2.0 GB) copied, 11.4032 seconds, 180 MB/s > root@Arzamas:~# > > > root@Arzamas:~# dd if=/dev/raid10/space of=/dev/null bs=1M count=2000 > 2000+0 records in > 2000+0 records out > 2097152000 bytes (2.1 GB) copied, 25.7089 seconds, 81.6 MB/s > root@Arzamas:~# > Try to increase the read-ahead size of your lvm devices: blockdev --setra 8192 /dev/raid10/space or increase it at least to the same size as of your raid (blockdev --getra /dev/mdX). Hope it helps, Bernd - 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
