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Archive Bit Vs. Modified Time

With Backup Exec 10.0, what are the advantages and disadvantages of using Archive Bit vs. Modified Time for full and incremental backup, and do  these options have any effect specifically to backing up Exchange Mailboxes.  

I am concerned about the size of my backup jobs. The full backup of my mailboxes are 135 GB, and the incremental is 100 GB. Should I not be seeing much smaller backups for my incremental?
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ejunge
Asked:
ejunge
1 Solution
 
peakpeakCommented:
Assume that all data has changed, then the sizes would be almost equal, so if most of tha data has changed they're almost equal in size.
Full backup doesn't care for the file time or archive bit, it just copies the lot to the backup media.
Archive bit tells that the file has been modified since an undefined time in the past so BE will grab it to the backup. You have two options here, one to reset archive bit and one to keep it. If you reset it and the file is not changed at the time of the next incremental backup it will not be included. I believe that's the option you want.

File modification time will make BE compare the file time on disk with that on the backup media (takes longer)

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SembeeCommented:
If you are backing up mailboxes instead of the information store then I am not surprised you are concerned about the backups.
However mailbox backups are close to useless for most disaster recovery scenarios. When it comes to Exchange I never do incremental backups, only full backups.

Simon.
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peakpeakCommented:
sembee, backing up mailboxes? You mean the old brick level ?
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SembeeCommented:
Brick level backup. When i see someone say mailboxes instead of information store that is what I tend to think of.

Simon.
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peakpeakCommented:
OK, we don't use that anymore :)
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Iamthecreator OMAdministrateur Systeme et ReseauxCommented:
Archive bit and Modified Time is almost the same
no effect on Exchange as there you backup the Transaction logs
the feature is there so that you can select the option for modified time where there are no Archive bits

Archive Bit

Whenever a file is created or changed, the operating system activates the Archive Bit or
modified bit. Unless you select to use backup methods that depend on a date and time
stamp, Backup Exec uses the archive bit to determine whether a file has been backed up,
which is an important element of your backup strategy.
Selecting the following backup methods can affect the archive bit:
  Full - Back up files - Using archive bit (reset archive bit)
  Differential - Back up changed files since last full - Using archive bit (does not reset
archive bit)
  Incremental - Back up changed files since last full or incremental - Using archive bit
(reset archive bit)
Whenever a file has been backed up using either the Full - Back up files - Using archive
bit (reset archive bit) or Incremental - Changed Files - Reset Archive Bit backup
method, Backup Exec turns the archive bit off, indicating to the system that the file has
been backed up. If the file is changed again prior to the next full or incremental backup,
the bit is turned on again, and Backup Exec will back up the file in the next full or
incremental backup. Backups using the Differential - Changed Files backup method
include only files that were created or modified since the last full backup. When this type
of differential backup is performed, the archive bit is left intact.

Modified Time
If you select to use Full - Back Up Files - Using modified time, Differential - Using
modified time, or Incremental - Using modified time, Backup Exec uses a files modified
time rather than the archive bit to determine if it needs to be backed up.
When Backup Exec runs a full or incremental backup, the time the backup launches is
recorded in the Backup Exec database. The next time an incremental or differential
backup launches, Backup Exec compares the file system time to the backup time recorded
in the Backup Exec database. If the file system time is later than the database time, the
file is backed up.
Note The Full - Using modified time backup method adds the time of the backup to the
Backup Exec database only if the full backup job completes successfully. If the full
backup job does not complete successfully, any subsequent backup jobs that use
the differential or incremental modified time backup methods back up all of the
data instead of just the data that changed since the last full backup.
About backup strategies
When an incremental backup is run, a new time is recorded in the Backup Exec database.
The database time is not updated with differential backups.
Using the modified time allows Backup Exec to run differential backups on file system,
such as Unix, which do not have an archive bit.
If you want Backup Exec to use modified time to determine if a file has been backed up,
the full and incremental (or full and differential) backups must use the same backup
selection list.
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Computer101Commented:
Forced accept.

Computer101
EE Admin
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