On Thu, Jun 29, 2006 at 06:15:23PM +0200, Dieter St?ken wrote: > Cristian Livadaru wrote: > > me again ... isn't there anybody that could give ANY hint on what's > > wrong? > > > > I did some test with dd and the result is terrible! > > > > LVM > > explendidos:/shared# dd if=/dev/zero of=test1.dd bs=64 count=1000 > > 1000+0 records in > > 1000+0 records out > > 64000 bytes transferred in 20.019969 seconds (3197 bytes/sec) > > seems the data gets written synchronously without any buffering. > Thus each write is delayed until the data is really written to > disk. For a 5400 RPM disk you get 90 transactions per seconds. > This gives about 10 seconds for 1000 chunks. "bs=64" means > 64 bytes! so each sector will be written multiple times. > So may be the system even reads in each sector again each time > before writing it, thus it takes two turns which gives 20 seconds. > > Unfortunately I can't tell why this happens :-( > > May be "direct IO" takes place (like for oflags=direct), where could I check this? > or this is some configuration option of LVM, i don't know about. > Try using "hdparm" to see, if DMA etc. is enabled. Have a look no matter how it's set, the result is always the same. I could'nt find any usefull information in any logfiles, I enabled LVM verbose mode and debug output but still nothing was found. > into /var/log/messages or use "dmesg" for nay hardware problems. > I recently discovered the "blockdev" command. Do you use any special I have read in some posts on the mailinglist about blockdev but not quite sure on how I could use it to solve my problem. > ext3 feature? You may try "tune2fs -o journal_data_writeback". > If you don't have relevant data on the LV, you may try to write > to the LV device directly. Is it slow for read, too? try "hdparm -t" hdparm -t /dev/share/sharevg /dev/share/sharevg: Timing buffered disk reads: 146 MB in 3.01 seconds = 48.50 MB/sec HDIO_DRIVE_CMD(null) (wait for flush complete) failed: Inappropriate ioctl for device I tried tune2fs but it didn't get any better. I also dont understand why with kernel 2.4 I get about 5mb/s instead of the 350kb/s not that 5mb would be great but still, much better then 350kb/s Maybee I should mention that this is some "want-to-be" raid controler that was on the mainboard. 0000:00:0e.0 RAID bus controller: Triones Technologies, Inc. HPT374 (rev 07) Cris _______________________________________________ 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/
