I was scratching around with I/O Analyzer v 1.0 and noticed that the IOmeter profiles that you provide appear to align on sector boundaries (i.e. 512b). I believe this is the default setting with IOmeter if it is not specified in your icf file. For example from 32k_50read_100rand.icf:
'ACCESS SPECIFICATIONS ========================================================= 'Access specification name,default assignment 32k; 50% Read; 100% Random, NONE 'size,% of size,% reads,% random,delay,burst,align,reply 32768,100,50,100,0,1,0,0 'END access specifications
esx# vscsiStats -t -s -w 8385874 -i 8313 esx# vscsiStats -t -s -w 8385874 -i 8313vscsiStats: Starting Vscsi stats collection for worldGroup 8385874, handleID 8313vscsiStats: Starting Vscsi cmd tracing for worldGroup 8385874, handleID 8313<vscsiStats-traceChannel>vscsi_cmd_trace_8385874_8313</vscsiStats-traceChannel>Success.esx# logchannellogger vscsi_cmd_trace_8385874_8313 /vmfs/volumes/vmhost-Local/aligned.trc &<I/O Analyzer 4096b aligned run here> esx# vscsiStats -x esx# vscsiStats -e /vmfs/volumes/vmhost-Local/aligned.trc > aligned.txt
Here are the results of the two runs.
First run is non-aligned using a modified version of the default icf's provided (align=0):
'ACCESS SPECIFICATIONS =========================================================
'Access specification name,default assignment
12k; 33% Read; 100% Random, NONE
'size,% of size,% reads,% random,delay,burst,align,reply
12288,100,33,100,0,1,0,0
'END access specifications
Alignment check:
[root@vmtst-ads-control traces]# cat nonaligned.iometer.txt | perl ../parse-trace.pl
Total IOs: 718549, 4K aligned: 89815, not 4K aligned: 628734
Second run is aligned (4K/4096b) using a modified version of the default icf's provided (but with align=4096):
'ACCESS SPECIFICATIONS =========================================================
'Access specification name,default assignment
12k; 33% Read; 100% Random, NONE
'size,% of size,% reads,% random,delay,burst,align,reply
12288,100,33,100,0,1,4096,0
'END access specifications
Alignment check:
[root@vmtst-ads-control traces]# cat aligned.iometer.txt | perl ../parse-trace.pl
Total IOs: 828443, 4K aligned: 828443, not 4K aligned: 0
Summary of results (sample size of 1 each but no reason to test more samples in this case):
| Run | Total IOs | 4K aligned IOs | non 4K aligned IOs | % 4K aligned |
|---|---|---|---|---|
| default_IOAnalyzer_alignment | 718549 | 89815 | 628734 | 12.49% |
| 4096b_IOAnalyzer_alignment | 828443 | 828443 | 0 | 100% |
The 12.49% result makes sense because one would expect with random I/O and 512b alignment, 1 out of every 8 IOs would happened to be aligned on a 4K boundary (i.e. 4096/512 = 8 => 1/8 = 0.125 => 12.5%). You can even see we got slightly higher IO out of the aligned case although this could be attributable to something else (warm cache), but not atypical when dealing with misaligned performance results.
I checked all of the .icf files provided with IO Analyzer v 1.0 and they all have align=0 in the access specifications.
Here is my simple script to check alignment:
#!/usr/bin/perl
use strict;
# Simple script to check 4K alignment of vscsiStats trace output
#
# Example of how to collect vscsiStats trace output:
# vscsiStats -t -s -w 8385874 -i 8313
# vscsiStats -t -s -w 8385874 -i 8313
#<vscsiStats-traceChannel>vscsi_cmd_trace_8385874_8313</vscsiStats-traceChannel>
# logchannellogger vscsi_cmd_trace_8385874_8313 /vmfs/volumes/vmhost-Local/io.trc &
#<do the IO you want to trace here>
# vscsiStats -x
# vscsiStats -e /vmfs/volumes/vmhost-Local/io.trc > io.txt
# cat io.txt > this_script.pl
# Lance Braswell @lance_braswell
my $aligned_cnt = 0;
my $notaligned_cnt = 0;
my $cnt = 0;
my $sector = 512;
my $align_check = 4096;
my $lba_multiple = int($align_check/$sector);
while (<>) { chomp; if ( /^\d+,(\d+),\d+,(read|write),(\d+),(\d+)$/ ) { my ($sizeb,$op,$lba,$timeus) = ($1,$2,$3,$4); my $mod = $lba % $lba_multiple; my $value = $lba/$lba_multiple; if ( $mod ) { $notaligned_cnt++; } else { $aligned_cnt++; } $cnt++; }
}
print "Total IOs: $cnt, 4K aligned: $aligned_cnt, not 4K aligned: $notaligned_cnt\n";
Lance Braswell