Please advise - Why IOPS by IOMeter is much slower than windows multi-threading data fetch IOPS?

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Please advise - Why IOPS by IOMeter is much slower than windows multi-threading data fetch IOPS?

Nai yan zhao
      Can anybody help me a little out of my difficulty? 

      I have a SSD and I am trying to use it to simulate my program I/O performance, however, IOPS calculated from my program is much much faster than IOMeter. 

      My SSD is PLEXTOR PX-128M3S, by IOMeter, its max 512B random read IOPS is around 94k (queue depth is 32). 
      However my program (32 windows threads) can reach around 500k 512B IOPS, around 5 times of IOMeter!!! I did data validation but didn't find any error in data fetching. It's because my data fetching in order?

      I paste my code belwo (it mainly fetch 512B from file and release it; I did use 4bytes (an int) to validate program logic and didn't find problem), can anybody help me figure out where I am wrong? 

      Thanks so much in advance!!

Nai Yan. 

#include <stdio.h>
#include <Windows.h>

**  Purpose: Verify file random read IOPS in comparison with IOMeter    
**  Author:  Nai Yan
**  Date:    Feb. 9th, 2012

//Global variables
long completeIOs = 0; 
long completeBytes = 0;
int  threadCount = 32;
unsigned long long length = 1073741824;                  //4G test file

int interval = 1024;

int resultArrayLen = 320000;

int *result = new int[resultArrayLen];

//Method declarison
double GetSecs(void);            //Calculate out duration
int InitPool(long long,char*,int);         //Initialize test data for testing, if successful, return 1; otherwise, return a non 1 value. 
int * FileRead(char * path);
unsigned int DataVerification(int*, int sampleItem);                  //Verify data fetched from pool

int main()
int sampleItem = 0x1;
char * fPath = "G:\\workspace\\4G.bin";
unsigned int invalidIO = 0;

if (InitPool(length,fPath,sampleItem)!= 1)
   printf("File write err... \n");

//start do random I/Os from initialized file
double start = GetSecs();

int * fetchResult = FileRead(fPath);
double end = GetSecs();

printf("File read IOPS is %.4f per second.. \n",completeIOs/(end - start));

//start data validation, for 4 bytes fetch only

// invalidIO = DataVerification(fetchResult,sampleItem);

// if (invalidIO !=0)
// {
// printf("Total invalid data fetch IOs are %d", invalidIO);
// }

return 0;

int InitPool(long long length, char* path, int sample)
printf("Start initializing test data ... \n");

FILE * fp = fopen(path,"wb");

if (fp == NULL)
printf("file open err... \n");
exit (-1);

else //initialize file for testing

for (int i=0; i<length; i++)


fp = NULL;

printf("Data initialization is complete...\n");

return 1;


double GetSecs(void)

    LARGE_INTEGER frequency;
    LARGE_INTEGER start;

    if(! QueryPerformanceFrequency(&frequency)) 
        printf("QueryPerformanceFrequency Failed\n");

    if(! QueryPerformanceCounter(&start))
        printf("QueryPerformanceCounter Failed\n");
return ((double)start.QuadPart/(double)frequency.QuadPart);

class input
char *path;
int starting;

input (int st, char * filePath):starting(st),path(filePath){}


DWORD WINAPI FileReadThreadEntry(LPVOID lpThreadParameter)
input * in = (input*) lpThreadParameter; 

char* path = in->path;

FILE * fp = fopen(path,"rb");

int sPos = in->starting;

// int * result = in->r;

if(fp != NULL)
fpos_t pos;
for (int i=0; i<resultArrayLen/threadCount;i++)

pos = i * interval;
//For 512 bytes fetch each time
unsigned char *c =new unsigned char [512];
if (fread(c,512,1,fp) ==1)
delete c;

//For 4 bytes fetch each time
/*if (fread(&result[sPos + i],sizeof(int),1,fp) ==1)

printf("file read err...\n");

fp = NULL;

printf("File open err... \n");

int * FileRead(char * p)
printf("Starting reading file ... \n");
HANDLE mWorkThread[256];                      //max 256 threads
completeIOs = 0;
int slice = int (resultArrayLen/threadCount);

for(int i = 0; i < threadCount; i++)
mWorkThread[i] = CreateThread(
(LPVOID)(new input(i*slice,p)),

   WaitForMultipleObjects(threadCount, mWorkThread, TRUE, INFINITE);
   printf("File read complete... \n");

   return result;


unsigned int DataVerification(int* result, int sampleItem)
unsigned int invalid = 0;
for (int i=0; i< resultArrayLen/interval;i++)
if (result[i]!=sampleItem)
invalid ++;

return invalid;

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