Thanks for your reply.
A typical example of my needs is as follows.
I took over as manager of an organisation.
As I was looking around in the computer room I saw the main server running in its rack, but in the corner of the room, on a table, I saw two old NT4 servers that were not powered up, not plugged in to anything and not running. I asked our IT support guys about them but the IT guys said they were redundant, and that I did not need to be concerned about them because all the files on the old servers had been copied to the new server. They advised that the old servers should just be dismantled and thrown away.
And besides that, they said that they did not have the old NT4 Admin passwords so the could get the oldservers to run even if they wanted to
But I am a skeptical type and I don’t just “accept” answers like that without checking.
I powered up the newer of the two old servers, bypassed the NT4 password security system and copied all the files on it to an external drive. Then I ran a duplicate check program to list all duplicate files on that old server AND the new server.
Then I ran my own macro which sorts through the groups of duplicates and then for every file that is on oldserver, if a copy of it exists on newserver, then delete the copy on oldserver. Oldserver should then only have files on it that are NOT on Newserver. Oldserver had about 600,000 files on it and Newserver had about 750,000 files.
Therefore, after the deletion macro runs there should be no files still on oldserver exceot older copies of recently-edited files.
But that was not what I found. I found about 20,000 files left on oldserver that were not on newserver!!
I weeded out about 12,000 as being unneeded junk (application install files, tmps, device drivers, etc) ,and another 5,000 as old copies of recently edited files, but there were still about 3,000 files left. They turned out to be extremely important financial and operating data and reports that had not been copied from oldserver to newserver, despite the confident assurances from my IT support people that all files had been copied across.
These uncopied reports and financial files contained critical information that the financial future of this $200 M/year company depended on.
Hence my skepticism was justified, as was my need for a robust and reliable duplicate finder.
Duplicate finders are NOT just for liberating file space. They are extremely important forensic tools for examining large numbers of files.