Full Backup /w Archive bit Backup Question

Posted on 2009-04-06
Last Modified: 2013-12-01
I need clarification on a specific backup scenario  Our drive storage unfortunately exceeds our backup tape capacity @ 20gigs.  This makes me have to replace a tape 2 to 4 times to do a full backup, and then if I have it on "verify", I'm popping the tapes in and out like 4 to 8 times total.  

This is extremely time consuming, so I have thought of a new plan.  Will this scenario work:  Full backup w/resetting archive bit on Drive X with one tape and do another Full Backup w/ resetting archive bit on Drive Z, and so on with other Tapes and Drives.  I then want to have a differential backup tape that backups both Drive X and Drive Z and possibly the other drives.  Will this work?  My fear is that the differential won't backup the correct files since I reset the archive bit at different times on the two drives.


Question by:T0DD
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LVL 16

Expert Comment

ID: 24082015

Backup OS and Program Files (static files) on weekends.
Backup data on week days.

If Data alone still is more than one full tape...make sure your compression is on and working.

Author Comment

ID: 24082739
Data is about 60 gigs.  I usually do a Shadow Copy monthly.

I guess I just need clarification that when you choose to reset the archive bit with two separate jobs, with two different drives and then choose to run a differential that encompasses both drives, will the correct information get backed up?

LVL 16

Expert Comment

ID: 24082859
Your archive bit method sounds subject to error over the long term.
Why not test it on a data  subset, then implement it if works.
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Author Comment

ID: 24082902
Would I like to know if anyone has tried this over the long term.  I know if I test it, I'll get results but long term examples is what I'm looking for.

LVL 10

Accepted Solution

itprotocall earned 250 total points
ID: 24086021
"My fear is that the differential won't backup the correct files since I reset the archive bit at different times on the two drives."

archive bit is not time-dependent so the fact that the two drives' full backup was done at different times will not affect the data that gets backed up. whatever files changed after they got backed up will be included in teh differential.

8AM - Drive X full backup - the archive bits for all the files are cleared
8 PM - Drive Y full backup - archive bit cleared for all files

now suppose you do a differential backup 8 AM next day:
for Drive X - whatever files got altered, added in last 24 hours will have archive bit set - these are included in the differential backup
for Drive Y - whatever files got altered, added in last 12 hours will have archive bit set - included in differential backup.

as you can see in the example, the number of files backed up in the Drive X's differential may be higher than the number of files in Drive Y's diff backup... (that also depends on your 'rate of change')

bottom line is you do not need to worry about the 'correct' files being backed up as the file attribute of 'archive bit' is handled by the windows file system and is quite reliable.

hope this is clear.


Author Closing Comment

ID: 31567261
Exactly what I was looking for.  Thank you!

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