Hi Jack!
Before we started using ADSM we ran a backup application called ESM on our
MVS mainframe. It was one of the most sophisticated backup applications at
that time (1993). It was created by a company called Legent and later on
Legent was bought by Computer Associates. They relabeled it to CA-ESM and
now (but I don't know this for sure) it's called BrightStor.
This product did what you mentioned. It stored all files just once, so the
winfile.exe file was only stored once for all Windows clients. The problem
with this approach was that the actual scan process involves some kind of
CRC check. Just checking the attributes and file size is not enough to
determine whether a file has changed. This scan took far to much time. Also,
since some files are identical during backup to version backed up earlier
on, your storage pool gets heavily fragmented and thus, a restore took a
very long time to complete.
Also, storage is getting cheaper and cheaper, so why bother?
Kindest regards,
Eric van Loon
KLM Royal Dutch Airlines
-----Original Message-----
From: Coats, Jack [mailto:Jack.Coats AT BANKSTERLING DOT COM]
Sent: Monday, September 13, 2004 22:25
To: ADSM-L AT VM.MARIST DOT EDU
Subject: Wishlist Item
Yes, I know I am dreaming, but...
An open source program, pcbackup or backuppc something like that on
Sourceforge has a very nice feature.
If a file is already backed up, it only keeps one copy of that file for ALL
its clients! What technique does it use to figure out if the files are
identical without comparing them? I didn't research it that far, but I
assume it uses something like file size and a checksum of some kind.
Anyway, if you have significantly identical client computer you are backing
up, just keeping one rather than N copies is better than any compression
known to man! It would be another field or so in the database for every
file, but it might be worth it! At least as an option.
... Jack
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