On Sat, Jun 14, 2003 at 10:07:54PM +0200, Herbert Poetzl wrote: > On Sat, Jun 14, 2003 at 02:45:11PM +0200, Svetoslav Slavtchev wrote: > > Quoting Herbert Poetzl <herbert@13thfloor.at>: > > > > > didn't say that this would be bad, only that > > > it live-locked my system at high load ... > > > the tenor on the list was: "highmem is bad" > > > so I turned it off, and, voila the system was > > > stable again ... > > > > snapshots + md + highmem is very bad > > if you don't use snapshots its perfectly OK > > I have to disagree, live-lock under high load is > not perfectly OK, at least not for me ... 8-) > > > > another, yet unexplained issue, is that on > > > another system, 4 SCSI discs, form a RAID 5 > > > array (software) which gives about 35MB > > > throughput, but lvm 1.0.7 ontop of that md > > > only has about 18MB throughput ... > > > > I've a bit defferent figures from a onboard HPT374 4 ide chanels with > > 4 IBM deskstars 80Gb, but i still lose 8-15Mb/s compared to plain md : > > > > /dev/hda: > > Timing buffer-cache reads: 128 MB in 0.41 seconds =308.43 MB/sec > > Timing buffered disk reads: 64 MB in 1.42 seconds = 45.07 MB/sec > > [root@svetljo root]# hdparm -tT /dev/md13 > > > > /dev/md13: > > Timing buffer-cache reads: 128 MB in 0.41 seconds =316.05 MB/sec > > Timing buffered disk reads: 64 MB in 1.08 seconds = 59.26 MB/sec > > [root@svetljo root]# hdparm -tT /dev/data > > data data2 > > [root@svetljo root]# hdparm -tT /dev/data2/Movies > > > > /dev/data2/Movies: > > Timing buffer-cache reads: 128 MB in 0.41 seconds =316.05 MB/sec > > Timing buffered disk reads: 64 MB in 1.32 seconds = 48.30 MB/sec > > I posted my results a month ago, but I digged them > out again, because together with your results, it > sheds new light on that issue ... > > mine raw disc md(raid5) lvm on md > ----------------------------------------------------- > hdparm 14694.40 34129.92 18667.52 > dd 1024k 14988.22 34732.56 18647.98 > dd 32k 15516.06 33945.48 18862.67 > > yours raw disc md(raid5) lvm on md > ----------------------------------------------------- > hdparm 46151.68 60682.24 49459.20 > > in both cases the lvm lies about 3MB over the raw > disc throughput, regardless of the md values ... The reason probably is LVMs read ahead. > > maybe this could lead to some explanation of this > issue ... unfortunately there was no reply to my > posting over the last month *sigh* > > best, > Herbert > > > time dd if=/dev/zero of=/mnt/Movies/BigFile.tm bs=1M count=4000 > > 4000+0 records in > > 4000+0 records out > > 0.02user 15.57system 1:37.10elapsed 16%CPU (0avgtext+0avgdata 0maxresident)k > > 0inputs+0outputs (148major+40minor)pagefaults 0swaps > > > > best, > > > > Svetljo > > > > > > _______________________________________________ > > linux-lvm mailing list > > linux-lvm@sistina.com > > http://lists.sistina.com/mailman/listinfo/linux-lvm > > read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/ -- Regards, Heinz -- The LVM Guy -- *** Software bugs are stupid. Nevertheless it needs not so stupid people to solve them *** =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- Heinz Mauelshagen Sistina Software Inc. Senior Consultant/Developer Am Sonnenhang 11 56242 Marienrachdorf Germany Mauelshagen@Sistina.com +49 2626 141200 FAX 924446 =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- _______________________________________________ linux-lvm mailing list linux-lvm@sistina.com http://lists.sistina.com/mailman/listinfo/linux-lvm read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
