Does "Differential/Modified time" works as advertised?

[fraxx]

I haven't used Backup Exec for quite a few years, but recently I've started to delve into what the latest version 9.1 brings to the table.
One thing I noticed is the feature of using Full, incremental and differential backups based on modified time instead of the old way of using the archive bit.
I tried the following:
I created a folder with 10.000 48k files and did a "FULL - Back Up Files - Allow incrementals and differentials using modified time". This went well

I then used a small "touch" utility to update the last modify time on 10% of the files.

I then did a "INCREMENTAL - Using modified time" and as expected I backed up the same 10% of the files.

I repeated the touch process, but I made sure I touched a different 10% of the files. I also repeated the "INCREMENTAL - Using modified time" backup.
I did this in total of three times, and each incremental backup generated 10%, as expected.

Now I did a "DIFFERENTIAL - Using modified time". According to the manual, this should backup all changed files since the last full backup. I interpret this to mean that a "DIFFERENTIAL - Using modified time" backup should in my case now backup 30% of the files.

It does not. In fact, nothing gets backed up.

Had I used the older method, where an incremental resets the archive bit I would fully agree that a following differential backup would not backup anything, since it uses the archive but. The point to my experiment was to make sure the new version of a differential backup would infact backup all modified files since last _full_, regardless of any incrementals inbetween.

I'm at Backup Exec 9.1 sp1, I updated the RAWS on my target server as well.

I use the same selection list for all three jobs (full, incr, diff).

I access the files through the default share, not through any user defined share.

I backup to disk, but that shouldn't make any difference.

Any help is greatly apprectiated.
/charles

 

[justin2000]

Seriously why are you bothering with the modified time method if you are backing up files which have an archive bit?

The modified time method was designed and should be used for file systems that do not have an archive bit.

 

[fraxx]

Many other backup packages have this feature. Legato NetWorker, HP Data Protector and Veritas NetBackup come to mind. So my question is part academic, to find out if Backup Exec also can do this.

My other angle on this is a backup scheme I use for NetWorker, and by reading the manual for Backup Exec I figured I could adapt it for use with Backup Exec, although slightly simpler.
It goes something like this:
Start with a full backup on a weekend.
Do incrementals during the weekdays
Do a modifired time differential next weekend.
Do incrementals the following weekdays.
Repeat for two more weeks until on the fourth weekend you do another full.
This way I get a fairly good balance with backup times, the amount of data I have to retain, while at the same time get a reasonably low number of restores I have to do in case I lose an entire volume or server.

The key issue here that the weekend differential must backup all files since the last full, else there's not much point. The manual clearly states this, but in my experiment it does not work as far as I can see.

/charles

 

[justin2000]

I would say this is a typo - or maybe Veritas thinks that what you are trying to do is overly complex? Possibly is?
What I say this is - the manual for Differential using archive bit says:-

DIFFERENTIAL - Changed Files. Includes all files that have
changed (based on the archive bit) since the last full backup, and does not affect any media rotation scheme because the archive bit is not reset.

Now what that should say is "since the last full backup or last incremental"

The DIFFERENTIAL - Using modified time - should say the same thing.

Now for what you want to do, I am wondering if you choose the option - Use the Windows Change Journal if available
"Select this option if you want to use Windows’ NTFS Change
Journal to determine which files have been modified since the last
full backup. This option can only be used with NTFS volumes and
only when the backup method selected is FULL - Back Up Files -
Allows incrementals and differentials using modified time,
DIFFERENTIAL - Using modified time or INCREMENTAL - Using
modified time."

Reading the BE manual, when it goes on about backup strategies, it is always Differential or Incremental - possibly again to provide for simplicity.

All that being said, maybe it is just a bug that needs to be fixed

 

[fraxx]

I tried both with and without "Use windows change journal if available". Same results.

The full and incrementals based on time work though. The full backup doesn't reset the archive bit, and the incrementals do indeed only backup the changed files. The time based incremental doesn't reset the archive bit either.
After the incrementals have run, all archive bits are still in place.

And Backup Exec being a basically simple product, adding on more or less half-baked features and options to make a backup administrators day interesting to say the least, that I can agree on.
/charles

 

[fraxx]

After having a rather good email dialogue with Veritas support we finally arrived at the conclusion:
This is the way Backup Exec works, it's by design that the differential backup doesn't pick up the changed files since it had already been backed up the incremental. Oh well.
/charles