benchmark_storage_quick_ioping

#!/usr/bin/env bash

#
# Trivial disk read test to measure latency
#

# Al Tolbey's page - https://tobert.github.io/post/2015-01-22-ioping.html
# Man - https://www.systutorials.com/docs/linux/man/1-ioping/ 

# test should be big enough to flood the buffering of the system and use the direct io flag if you dd supports ig
BLOCKSIZE=10240000
BLOCKCOUNT=10
#BLOCKCOUNT=150

export thisCommand=`basename $0`

if [ x"$1" == x ]; then
	echo "Error: missing directory name"
	echo "Usage: $thisCommand dir"
	exit 1
else
	dirName="$1"; shift
	if [ ! -d "$dirName" ]; then echo "No such dir: $dirName"; exit 1; fi
fi


set -x

:
: Read test
:
ioping -c $BLOCKCOUNT -s $BLOCKSIZE -D "$dirName"

# -D option not supported on OSX. Required for O_DIRECT

# Todo:
# From: http://askubuntu.com/questions/122857/can-i-copy-large-files-faster-without-using-the-file-cache
#
# There is the nocache utility, which can prepended to a command like ionice and nice. 
# It works by preloading a library which adds posix_fadvise with the POSIX_FADV_DONTNEED flag to any open calls.
#
# In simple terms, it advises the kernel that caching is not needed for that particular file; the kernel will then 
# normally not cache the file. See here for the technical details.
#
# It does wonders for any huge copy jobs, e. g. if you want to backup a multi terabyte disk in the background
#  with the least possible impact on you running system, you can do something along
#  > nice -n19 ionice -c3 nocache cp -a /vol /vol2.
#
# A package will be available in Ubuntu 13.10 and up. 
# If you are on a previous release you can either install the 13.10 package or opt for this 12.04 backport by François Marier.
# See: https://launchpad.net/ubuntu/+source/nocache
# And: https://launchpad.net/~fmarier/+archive/ubuntu/ppa/+index?field.series_filter=precise&batch=75&memo=75&start=75