I have recently added a WD 2TB green drive to two systems and am finding terrible performance with btrfs on an LVM using these drives.
I just saw on the mythtv list about the sector size problem these drives have where they have poor performance unless you can map the partitions onto certain sector boundaries. My problem is that LVM2 is not supported in parted which is the recommended tool to deal with this. How can I map an lvm with 4 or more disks, only one of which is a "WD Green drive" and containing multiple reiserfs and btrfs file systems for best performance. As these drives look useful in a data centre because of their power savings, I presume someone must have solved this already! I suspect I only need to map the individual PE to a particular start sector on each drive, not btrfs, but then there is stripe/block sizes to consider as well ... WD also are recommending 1mb sector boundaries for best performance - I can see a reinstall coming up :) Is there an application that can analyze a disk for settings and automatically list the best/recommended settings? This should be scriptable anyway so I may end up going this way if someone hasn't gone there first. Yesterday, a backup using dirvish that used to take 3-5 minutes to a reiserfs partition on lvm on an older disk took nearly 19 minutes to the same server, same lvm but on a btrfs partition on the new WD drive the lvm was extended onto. Delete performance is even worse :( BillK
