Offer Baruch, You can try two apps to benchmark your disks:
1 - bonnie++ - http://www.coker.com.au/bonnie++/ 2 - iozone - http://www.iozone.org/ Both are simple to install and use. Those software will give you performance numbers. When using bonnie++, you need to use(at least) twice disk space than you have RAM. If you have 1GB of RAM then you need to use 2GB of disk. This is important to avoid wrong performance values due Linux cache. Peter 2009/8/4 עופר ברוך <[email protected]>: > Hi all, > > I have a big performance problem running Redhat V5.2 on system z. > The configuration looks like this: > I gave the test Linux an absolute share of 50% (limithard) so cpu won't vary > from one test to the other (I have 1 IFL on a z9 BC machine) > Linux has 1GB of RAM – no paging from the VM side or Linux size (this is a > test guest with nothing on it). > I am using model-3 ECKD disks using Hitachi disks. No PPRC is involved. We > have 4 Ficon chpids connected to the z/VM (shared with z/OS. Ficons > utilization at about 10%). > > For the problem itself… > I received bad performance reports from my dba (using oracle 10g on z/Linux) > - a simple create table space of 300MB takes about 40 seconds… > Another test to create the same table space on a tmpfs took 2 seconds. > So, I figured that the problem is I/O related and not Oracle related… > Note: before every test I run the following commands to clear the cache: > sync; echo 3 > /proc/sys/vm/drop_chaches; sync > I then tried the following command in order to write directly to the device: > dd if=/dev/zero of=/dev/dasd bs=4096 count=75000 (about 300M) > I receive 200-400MB per second. So far so good. > I then tried to do the following (writing to the partition): > dd if=/dev/zero of=/dev/dasd1 bs=4096 count=75000 (about 300M) > I receive 60-90MB per second. > I then tried writing to a file system: > dd if=/dev/zero of=/oracle/datafiles/big_file.txt bs=4096 count=75000 (about > 300M) > I receive 10-30MB per second. > I did many more tests… writing to a file system that resides directly on the > dasd/partition/lvm/lvm with striping etc… > All returned very bad performance. > I also tried writing to the dasd/partition on SLES and received the same > results. Very good performance writing directly to the disk very bad > performance writing to the partition. > I also tried writing to the dasd/partition on a native LPAR and received the > same results. > > Any thoughts? > Is my test case ok? Am I doing something wrong? > Is this normal behavior? > > I expect z/Linux to give me great I/O performance… What's wrong? > > Thanks! > Offer Baruch > > ---------------------------------------------------------------------- > For LINUX-390 subscribe / signoff / archive access instructions, > send email to [email protected] with the message: INFO LINUX-390 or visit > http://www.marist.edu/htbin/wlvindex?LINUX-390 > ---------------------------------------------------------------------- For LINUX-390 subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390
