Backup Exec + offsite backups

[eelali]

Hello everyone, first time poster

Anyways, my corporation is running backup exec for Windows Servers versions 11 and 12, and i have been recently tasked with implementing off-site backups.  We have there sites, and each site is backing up weekly 500 gig fulls, and 100 gig differentials.   We do not have a fiber connection, and even if we did, that still might be pushing it for off-site backups.

In any case, I've been researching data deduplicaiton as a solution (symantec does have an add-on for this)- and i'm at a cross roads of whether this will help increase efficiency with storage, or will it also reduce the amount of traffic passed over the wire?  

If it does, then I have another dillemma... the backup exec team keeps telling me that incremental backups will only transfer the CHANGED bits- but what I keep seeing through various tests, including testing with wireshark, is that the entire file is backed up again if the archive bit is overwritten (i.e, if the file is modified)- and NOT only the bits that have changed are transfered.

So can somebody please enlighten me?  Because so far, I am NOT convinced from what the symantec support team has told me, and it seems that if a file is modified, the ENTIRE FILE is copied over the wire.

Also, if data de duplication will decrease the amount sent over the wire, or just the amount stored?

Thanks

[eelali]

 anyone?  I basically just want to know if incremental backups transfer the entire changed file once the archive bit has been modified, or just the bits that have changed. and if it's just the bits that have changed, why are my tests indicating otherwise?

[Larry_Fine]

If you are talking about files (not databases) the whole file is backed up when it changes.  I don't know about databases... that might be more efficient and they may have ways to only get changes there.

[eelali]

 that's what i thought, but do you have a source for this?  my coworker was told otherwise, and when i called symantec, they kept telling me that only bits that have changed are backed up and i'm 99% certain that this is NOT the case

[Ken_Putnam]

An INCR  backs up only files that have changed since the last full or incremental backup, but it backs up the entire file that has changed

See the glossary near the back of hte Admin Guide

[eelali]

 ok, so...it's NOT only the bits that are transfered over the wire? the entire file is transferred over the wire?

(i mentioned it to my coworker, and he brought up the point that even by transferring just the bits that have changed, it "backs up the entire file that has changed". i don't have the admin guide, but in the help section, the verbage there doesn't specify if only the changed bits of the file are transferred to the backup server, where the file is recreated using the full backup located there, or if every bit of the changed file, and not just the changed bits are transferred over teh wire).

i did mention that the scenario in which the file is transferred ot the backup server would be debunked by the fact that non-autoloader tape drives don't need the full tape in order to backup changed files or restore changed files (only unchanged files), but he said it could be different for backup-to-disk solutions

[Ken_Putnam · Accepted solution]

 ok, so...it's NOT only the bits that are transfered over the wire? the entire file is transferred over the wire?

Correct
 
the verbage there doesn't specify if only the changed bits of the file are transferred to the backup server, where the file is recreated using the full backup located there, or if every bit of the changed file, and not just the changed bits are transferred over teh wire).


This sounds like a "synthetic" backup, where a new full is created from the last full and latest INCR, but that, again, refers to entire files, not changed bits of a file

If I understand the third paragraph, yes B2D is similar to B2T in this respect, since you can place FULLS and INCRs on removeable media and still get another true INCR without the latest FULL being mounted