09-18-2008
That is exactly why the answer(s) we gave to the original question were somewhat meaningless.
What you are seeing is only the effect of buffer size on the number of times underlying stdio system calls are made. More calls more overhead. Nothing to do necessarily with I/O throughput. Larger buffers do improve performance but there comes a point where doubling buffer size buys almost nothing.
The actual I/O throughput is a function of "hard drive" cache size - our drives are on a giant SAN with RAID support. Buffering is immense. So our "hard drives" are really just a frontend box that pretends it is a disk - fronting for a RAID cluster.
Clearing the cache just means you are measuring disk latency and seek times as well as the other components of I/O.
Last edited by jim mcnamara; 09-18-2008 at 05:44 PM..
10 More Discussions You Might Find Interesting
1. UNIX for Dummies Questions & Answers
Hi
I need to access files from a specific folder of a Linux system from an another Linux System Remotely.
I know how to, Export a folder on One SCO System & can access the same by using Import via., NFS in the Sco Unix SVR4 System using the scoadmin utility.
Also, I know to use mount -t ... (2 Replies)
Discussion started by: S.Vishwanath
2 Replies
2. Programming
INFO:
The program should enter a circle radius and Id for that circle to a file, then it should search for that id and print the radius for that circle.
PROBLEM:
This program compiles but it's not searching properly.
Circle.h
#ifndef CIRCLE_H
#define CIRCLE_H
#include <iostream>... (0 Replies)
Discussion started by: VersEtreOuNe
0 Replies
3. Cybersecurity
Hello,
i need some help/advice on how to solve a particular problem.
these are the users:
|name | group |
---------- ---------------
|boss | department1 |
|assistant | department1 |
|employee | department1 |
|spy | department2 |
this is the... (0 Replies)
Discussion started by: elzalem
0 Replies
4. Programming
I'm in the UNIX environment. I'd like to read a Microsoft Access MDB file, and write the contents of that file into an ASCII text file. I want to write a C program to do this.
Does anyone know if there's already source code out there that does this?
Please advise. Thanks. (3 Replies)
Discussion started by: serendipity1276
3 Replies
5. UNIX for Dummies Questions & Answers
hi all,
i want to know y kernel is giving access for multiple users to access a file when one user may be the owner is executing that file. Because other user can manipulate that file when the other user is executing that file, it will give the unexpected result to owner . plz help me... (1 Reply)
Discussion started by: jimmyuk
1 Replies
6. IP Networking
Hi
Good Day, i would like to ask for further info about my problems experiencing this evening. Im a PPP0 connection in the internet using 3G located in asia pacific region.i had this problem this evening in my INTERNET connections that there are some sites i can't open example ( Gizmodo.com,... (2 Replies)
Discussion started by: jao_madn
2 Replies
7. UNIX for Dummies Questions & Answers
Hey friends,
If a file has permissions 000, then who can access the file? (1 Reply)
Discussion started by: paras.oriental
1 Replies
8. Solaris
Hi All,
I want to configure samba share permission so that only directory creator/owner has a read and write permission and other users should not have any read/write access to that folder.Will that be possible and how can this be achieved within samba configuration.
Regards,
Sahil (1 Reply)
Discussion started by: sahil_shine
1 Replies
9. Proxy Server
Dear all experts here,
:)
I would like to install a proxy server on Linux server to perform solely to control the access of Web server.
In this case, some of my vendor asked me to try Squid and I have installed it onto my Linux server.
I would like know how can I set the configuration to... (1 Reply)
Discussion started by: kwliew999
1 Replies
10. Shell Programming and Scripting
We have three files as mentioned below:
1. main_file.txt: This is the file in which all operations will be done. Which means this file will be signed by using the below two files
2. signature_file.txt: This is a status file and contains two signatures.
3. command.txt:file contains two commands... (2 Replies)
Discussion started by: chetanojha
2 Replies
LEARN ABOUT SUSE
file::randomaccess
File::RandomAccess(3) User Contributed Perl Documentation File::RandomAccess(3)
NAME
File::RandomAccess - Random access reads of sequential file or scalar
SYNOPSIS
use File::RandomAccess;
$raf = new File::RandomAccess(*FILE, $disableSeekTest);
$raf = new File::RandomAccess($data);
$err = $raf->Seek($pos);
$num = $raf->Read($buff, $bytes);
DESCRIPTION
Allows random access to sequential file by buffering the file if necessary. Also allows access to data in memory to be accessed as if it
were a file.
METHODS
new Creates a new RandomAccess object given a file reference or reference to data in memory.
# Read from open file or pipe
$raf = new File::RandomAccess(*FILE);
# Read from data in memory
$raf = new File::RandomAccess($data);
Inputs:
0) Reference to RandomAccess object.
1) File reference or scalar reference.
2) flag set if file is already random access (disables automatic SeekTest).
Returns:
Reference to RandomAccess object.
SeekTest
Performs test seek() on file to determine if buffering is necessary. If the seek() fails, then the file is buffered to allow random
access. SeekTest() is automatically called from new unless specified.
$result = $raf->SeekTest();
Inputs:
0) Reference to RandomAccess object.
Returns:
1 if seek test passed (ie. no buffering required).
Notes:
Must be called before any other i/o.
Tell
Get current position in file
$pos = $raf->Tell();
Inputs:
0) Reference to RandomAccess object.
Returns:
Current position in file
Seek
Seek to specified position in file. When buffered, this doesn't quite behave like seek() since it returns success even if you seek
outside the limits of the file.
$success = $raf->Seek($pos, 0);
Inputs:
0) Reference to RandomAccess object.
1) Position.
2) Whence (0=from start, 1=from cur pos, 2=from end).
Returns:
1 on success, 0 otherwise
Read
Read data from the file.
$num = $raf->Read($buff, 1024);
Inputs:
0) Reference to RandomAccess object.
1) Buffer.
2) Number of bytes to read.
Returns:
Number of bytes actually read.
ReadLine
Read a line from file (end of line is $/).
Inputs:
0) Reference to RandomAccess object.
1) Buffer.
Returns:
Number of bytes read.
Slurp
Read whole file into buffer, without changing read pointer.
Inputs:
0) Reference to RandomAccess object.
Returns:
Nothing.
BinMode
Set binary mode for file.
Inputs:
0) Reference to RandomAccess object.
Returns:
Nothing.
Close
Close the file and free the buffer.
Inputs:
0) Reference to RandomAccess object.
Returns:
Nothing.
AUTHOR
Copyright 2003-2010 Phil Harvey (phil at owl.phy.queensu.ca)
This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself.
SEE ALSO
Image::ExifTool(3pm)
perl v5.12.1 2010-01-04 File::RandomAccess(3)