Wow. Many deep bows of reverence for all that responded. As UK inferred, I was (indeed) doing something wrong. Based on the above suggestions, this was the script tested:

#!/usr/local/perl5.6.1/bin/perl -slw
use strict;
our $BUFSIZE ||= 2**30;
open my $fhi, '+<', "/data/p_dm200/ndm_ip_pull/test_customer1" or die $!;

while( sysread $fhi, $_, $BUFSIZE ) {
tr^M ;
sysseek $fhi, -length(), 1;
syswrite $fhi, $_, $BUFSIZE;
}
close $fhi;

which was tested against an 8,595,447,728 byte file. The time output was:
real 10m5.95s
user 1m48.55s
sys 0m17.24s

An amazing 10 minutes. I checked the output and it looks exactly as expected. I even retested 3 times and each time the results were similar.

Ok, now I am getting greedy and curious as to if this can be optimized more?? I ran top during this session and saw that SIZE and RES were both around 1026M throughout the duration and only 1 cpu seemed used. Would increasing BUFSIZE help performance linearly? If I was capable (and I am not) would either shared memory threads or parallel forks produce big gains? Any other low-hanging fruit?

Perlfan, the ROMIO seemed interesting but I could not find a perl sample. Still it seemed interesting. Anonymous Monk, please forgive my ignorance but what does HD mean?

A sincere thanks to all,
--Paul

In reply to Re^2: Muy Large File by BuddhaLovesPerl
in thread Muy Large File by BuddhaLovesPerl

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.