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 ... 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/ _______________________________________________ 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/
