przemolicc@poczta.fm wrote:

The above numbers are true if we have random (!) IO pattern. In case of sequential (!) IO even SATA disks can deliver much, much higher numbers.

sequential IO is remarkably rare in a typical server environment

anyways, the IOPS numbers on sequential operations aren't much higher, they are just transferring more data per operation.

Thanks for all the updates. Will look into iozone and the advice given about the rest.

2010/5/6 przemolicc@poczta.fm:

On Thu, May 06, 2010 at 12:56:55AM -0700, John R Pierce wrote:

...

przemolicc@poczta.fm wrote:

...

The above numbers are true if we have random (!) IO pattern. In case of sequential (!) IO even SATA disks can deliver much, much higher numbers.

sequential IO is remarkably rare in a typical server environment

Yes, of course: Oracle's redo logs which are key performance factor for all transactions (inserts/updates) have sequential IO pattern. And Oracle is not a typical server environment ....

...

anyways, the IOPS numbers on sequential operations aren't much higher, they are just transferring more data per operation.

I didn't say that they _are_ much higher. I said that even SATA disks can deliver hight IOPS on condition of sequential IO.

Regards Przemyslaw Bak (przemol) -- http://przemol.blogspot.com/

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There is a dd test that floats around the PostgreSQL lists, so I wrote this simple script to automate it - use at your own risk!

#!/bin/bash

# do something which parses command line parameters

DEFAULT_BLOCK=8 DEFAULT_PATH=/data/tmp DEFAULT_FILE=ddfile

helpme() { echo "Usage: $0 [RAM=x] [PATH=/foo/bar] [FILE=foo] [BLOCKSIZE=X]" echo "Runs a dd test on disk subsystem to benchmark I/O speed" echo " BLOCKSIZE - given in K. Should be no need to change" echo " default is 8 which is what PostgreSQL uses" echo " RAM - must be specified in Gigs" echo " default is to use output of 'free' command" echo " PATH - where do you want the files created? i.e. which filesystem do you want tested?" echo " default is $DEFAULT_PATH" echo " FILE - file name to create in test. Really makes no difference." echo " default is $DEFAULT_FILE" exit 1 }

default_ram() { MYB=`free | grep Mem: | awk '{print $2}'` ((MYG=MYB/1000/1000)) export MYGIGS=$MYG echo "RAM not specified - assuming ${MYB}/${MYGIGS}G" }

default_path() { export MYPATH=$DEFAULT_PATH echo "PATH not specified - using default $MYPATH" }

default_file() { export MYFILE=$DEFAULT_FILE echo "FILE not specified - using default $MYFILE" }

default_block() { export MYBLOCK=$DEFAULT_BLOCK echo "BLOCKSIZE not specified - using default $MYBLOCK" }

RAMGIVEN=0 PATHGIVEN=0 FILEGIVEN=0 BLOCKGIVEN=0

while [ $# -gt 0 ] do MYVAR=`echo $1 | awk -F= '{print $1}'` MYVAL=`echo $1 | awk -F= '{print $2}'`

case $MYVAR in BLOCKSIZE) MYBLOCK=$MYVAL BLOCKGIVEN=1 ;;

RAM) MYGIGS=$MYVAL RAMGIVEN=1 ;;

PATH) MYPATH=$MYVAL PATHGIVEN=1 ;;

FILE) MYFILE=$MYVAL FILEGIVEN=1 ;;

-h|-help|--h|--help) helpme ;;

*) echo "ERROR : unknown parameter [${MYVAR}]" ;; esac

shift done

[[ $RAMGIVEN -eq 0 ]] && default_ram [[ $PATHGIVEN -eq 0 ]] && default_path [[ $FILEGIVEN -eq 0 ]] && default_file [[ $BLOCKGIVEN -eq 0 ]] && default_block

PATH_EXISTS=0 [[ -d $MYPATH ]] && PATH_EXISTS=1

echo "[$MYGIGS][$MYPATH][$MYFILE][$PATH_EXISTS]"

mkdir -p $MYPATH pushd $MYPATH

df .

FREESPACE=`df . | tail -1 | awk '{print $4}'`

BLOCKSPERGIG=125000

((ONCERAM=BLOCKSPERGIG*MYGIGS)) ((TWICERAM=2*BLOCKSPERGIG*MYGIGS)) ((THRICERAM=3*BLOCKSPERGIG*MYGIGS*MYBLOCK))

echo "Have:$FREESPACE, Need:$THRICERAM (3x RAM)"

if [ $THRICERAM -ge $FREESPACE ] then echo "ERROR: not enough room on disk" echo "Have:$FREESPACE, Need:$THRICERAM (3x RAM)" exit 2 fi

DDCOM="dd if=/dev/zero of=${MYFILE} bs=8k count=${TWICERAM} && sync" echo $DDCOM

time sh -c "$DDCOM" DDCOM="dd if=/dev/zero of=${MYFILE}2 bs=8K count=${ONCERAM}" echo $DDCOM $DDCOM

DDCOM="dd if=${MYFILE} of=/dev/null bs=8k" echo $DDCOM time $DDCOM

rm -f ${MYFILE} rm -f ${MYFILE}2 [[ $PATH_EXISTS -eq 0 ]] && rmdir $MYPATH

popd

On 05/19/2010 02:44 AM, Matt Keating wrote:

2010/5/6 Matt Keatingkeatster@gmail.com:

...

Thanks for all the updates. Will look into iozone and the advice given about the rest.

Either I'm doing/reading something wrong or a 1TB SATA 7200 RPM drive is faster than 4x300GB SCSI 10K RPM drives in raid 10. Both of the results below were from iozone, running the following command: $ iozone -R -l 5 -u 5 -r 4k -s 100m -F /tmp/F1 /tmp/F2 /tmp/F3 /tmp/F4 /tmp/F5

[...]

Am I doing something wrong? Please advise.

I don't usually use iozone (I usually use bonnie++) so take this with a grain of salt, but those speed look suspiciously like cache speeds. Bump the size (-s parameter) up to twice your real RAM size.

From: Matt Keating keatster@gmail.com

...

I don't usually use iozone (I usually use bonnie++) so take this with a grain of salt, but those speed look suspiciously like cache speeds. Bump the size (-s parameter) up to twice your real RAM size.

Will give that a try - 16gb file incoming

Or maybe do a: sync; echo 3 > /proc/sys/vm/drop_caches between the 2 tests...?

JD

*Try dbench.* * * * http://publib.boulder.ibm.com/infocenter/lnxinfo/v3r0m0/index.jsp?topic=/lia... * * * *http://publib.boulder.ibm.com/infocenter/lnxinfo/v3r0m0/index.jsp?topic=/liaag/journalingfilesystem/publicjournal12.htm OR* * * *http://linuxhelp.150m.com/resources/fs-benchmarks.htm* * * * http://linuxhelp.150m.com/resources/fs-benchmarks.htm http://www.phoronix-test-suite.com/?k=home * -------------------------- Best Wishes, Waleed Harbi

Dream | Do | Be

On Wed, May 19, 2010 at 4:04 PM, Matt Keating keatster@gmail.com wrote:

...

I don't usually use iozone (I usually use bonnie++) so take this with a grain of salt, but those speed look suspiciously like cache speeds. Bump the size (-s parameter) up to twice your real RAM size.

-- Benjamin Franz _______________________________________________ CentOS mailing list CentOS@centos.org http://lists.centos.org/mailman/listinfo/centos

Will give that a try - 16gb file incoming :/ _______________________________________________ CentOS mailing list CentOS@centos.org http://lists.centos.org/mailman/listinfo/centos

On 05/05/2010 05:55 PM, Dominik Zyla wrote:

Try to run the same IO operations as your production server is running. Bonnie++ could be good application for benchmarking. Also run some parallel rsync, rm, find, etc proccesses.

I am with John Pierce on this one, role and app will dictate benchmarks that reflect reality.

Having said that, I think iozone > bonnie++

- KB

On May 5, 2010, at 1:13 PM, Les Mikesell lesmikesell@gmail.com wrote:

On 5/5/2010 12:00 PM, Karanbir Singh wrote:

...

...

Try to run the same IO operations as your production server is running. Bonnie++ could be good application for benchmarking. Also run some parallel rsync, rm, find, etc proccesses.

I am with John Pierce on this one, role and app will dictate benchmarks that reflect reality.

Having said that, I think iozone> bonnie++

If the job involves creating/deleting lots of little files like a mail server with maildir format storage, you might try to dig up a copy of postmark too.

I found iometer is a good tool for real-world benchmarking if you take the time to setup the tests according to the workload.

-Ross

2010/5/6 John R Pierce pierce@hogranch.com

??????? ???????? wrote:

...

Use a simple test: time dd if=/dev/zero of=/tmp/test-hd bs=1M count=1000

sequential cached writes, yeah, thats useful. *not*

This is one of the steps.

You can use sysbench random read and random write for multi-thirds.

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