On Thu, 2004-06-10 at 08:34, David Greaves wrote:Thanks to those that made suggestions.
Thanks
I'd tried that, but no real change. I started 1t 128k and also tried 64k, 256k :) (oh, and 1k)
I did some tests a few months ago with bonnie++.. might offer some encouragement (please don't post this to slashdot.. ;)
http://spamaps.org/raidtests.php
There's a lot of data there, but if you look at the LVM stuff, you might
notice that the concurrent performance (having 3 processes hammering the
disks in different places instead of just one) was quite good when
compared to flat out RAID5. I'll pay 5% performance for manageability
any day. :-D
In the end I used
blockdev --setra 4096 on all my devices (/dev/sda,b,c,d and the /dev/md0 and the /dev/video_vg/video_lv) and this doubled throughput.
I am reading multi-gigabyte video files so these parameters are not for everyone.
No-one ever replied as to why blockdev --setra / --getra is not the same as that displayed in lvdisplay
And it's not documented that I can find. There's a comment: "Not used by device-mapper." And that means.....?
It's ignored? not implemented yet? Good luck?
# lvdisplay /dev/video_vg/huge_lv --- Logical volume --- LV Name /dev/video_vg/huge_lv VG Name video_vg LV UUID 3kz7n9-97Rg-2LJw-J9ml-1BBS-jGs0-Onh4NI LV Write Access read/write LV Status available # open 1 LV Size 312.50 GB Current LE 5000 Segments 1 Allocation inherit Read ahead sectors 120 Block device 253:1
# blockdev --getra /dev/video_vg/huge_lv 4096
<sigh> Let this post be there for Google - the modern man-page for linux. (if you've got your fingers crossed!)
David _______________________________________________ linux-lvm mailing list linux-lvm@redhat.com https://www.redhat.com/mailman/listinfo/linux-lvm read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
