Backing up the large fileserver - Archive bit vs time stamp
We have large file server where the backup window extends over days. To reduce the backup windows, we are considering backing it up with one time Full backup, after that substituting with the cumulative on weekly basis and differntials on the weekdays.
There is note in the “Client Settings Properties for Windows Clients” help file as below:
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“Note: |
Symantec recommends that you do not combine differential incremental backups and cumulative incremental backups within the same Windows policy when the incremental backups are based on archive bit. |
As per recommendation, we are looking to use the timestamp method but would like to know of if there are any disadvantages of using time stamps vs Archive bit.
About Archive Bit vs Timestamp:
With Archive Bit selection, Cummulative will ONLY backup files with Archive bit set and miss all the changes since the last Full or Incremental.
Please see if this section in the manual answers your question:
How NetBackup determines that files are due for backup
On Windows clients, NetBackup performs the incremental backups of files that
are based on the Perform incrementals based on archive bit setting. This setting
is found in the Backup, Archive, and Restore client interface, under File >
NetBackup Client Properties, on the General tab.
If Perform incrementals based on archive bit is enabled, incremental backups
for this client are based on the state of the archive bit of each file. The operating
system sets the bit whenever a file changes and it remains set until cleared by
NetBackup. The conditions under which NetBackup clears the bit depend on the
type of backup being performed.■ For a full backup, NetBackup backs up files regardless of the state of their
archive bit. After a full backup, the archive bit is always cleared.
■ For a differential incremental backup, NetBackup backs up the files that have
the archive bit set and have therefore changed. When the client receives a
response from the server that indicates that the backup was successful (or
partially successful) the archive bits are cleared. The clear archive bit lets the
next differential incremental back up only the files that changed since the
previous full or differential incremental backup.
■ For a cumulative incremental backup, NetBackup backs up the files that have
the archive bit set. However, NetBackup does not clear the archive bits after
the backup. Without a clear archive bit, the next cumulative incremental
backup backs up changed files and the files that were in the cumulative
incremental backup.
If Perform incrementals based on archive bit is disabled, NetBackup includes a
file in an incremental backup only if the datetime stamp of the file has changed
since the last backup. The datetime stamp indicates when the file was last backed
up.
Depending on the timestamp, NetBackup behaves in the following manner:
■ For a full backup, NetBackup backs up files regardless of the datetime stamp.
■ For a differential incremental backup, NetBackup compares the datetime stamp
of the file against the last full or incremental backup.
■ For a cumulative incremental backup, NetBackup compares the datetime stamp
of the file against the last full backup.
If files are installed or copied from another computer, the new files retain the
datetime stamp of the originals. If the original date is before the last backup date,
the new files are not backed up until the next full backup.
