> I wonder how you handle RAID for your LV because in my experience LVM > RAIDs are very slow in comparison to mdadm RAID. I have issues like you > describe for guests running on LVM RAID (not using raw LV, though).
I'm using mdraid around LVM, so e.g. /dev/md1 (RAID1 with 2 disks) is being used as a PV. I never bothered to try LVM RAID1 as I am happy with mdraid and storing metadata on a third disk appears to be mandatory but seemed like too much overkill. Alignment should be okay as well. All disks involved on those servers have 4k sectors but I paid close attention while partitioning and initializing mdraid and LVM, so I am pretty sure sectors are aligned. Even if they wouldn't be it should not have such a serious impact, should it? It's only a few kB every few seconds coming from guests and I already have incredibly high latency so I doubt it could have anything to do with sector alignment. Daniel
