Forum Discussion

gjisrael1420's avatar
gjisrael1420
Level 3
13 years ago

Mixing Incremental and Differential backups

I am Using Symantec backup exec 2010 with the following backups:

full backups - last saturday of the month

Differential backups - last saturday of every week

incremetnal backups - end of every day.

suppose if i need do restore of the day on second monday of the month.

will restoring the the last full backup and last differential backup will restore the data? will the last differentail data holds all the data modified from the last full backup even if  incremental backups are also involved in the middle.

OR

do i need to restore the last full backup, then subsequent incremental and the differential backups.

2010
Backup and Recovery
Backup Exec
  • pkh's avatar
    pkh
    13 years ago

    will the last differentail data holds all the data modified from the last full backup even if  incremental backups are also involved in the middle.

    No.  The differential backup will only contain files modified since the last incremental backup or full backup. Incremental and full backups resets the archive bit.

    So in your case, if you need to restore something in the middle of the second week, you would need to restore the full backup plus the first week's incremental followed by the latest differential.

    It is a bad idea to mix differential and incremental backups because it can get confusing and confusion is the last thing you want when your server is down.  It is better to stick to a simple scheme like full + incremental or full + differential.  Better yet, just do full backups every time if your backup window permits.  Doing just full backups means that you only have one backup to restore and it is the fastest amongst all the methods.

    All the above is applicable regardless of whether you are using the modified time or archive bit methods.

7 Replies

Sort By
  • Kiran_Bandi's avatar
    Kiran_Bandi
    Level 6
    13 years ago

    Restoring last FULL and last DIFF will give you the data till saturday of that month.

    Are you using modified time to take inc/diff backups?

    Regards....

  • gjisrael1420's avatar
    gjisrael1420
    Level 3
    13 years ago

    No, i am usning Archive bit reset.

    if i am using archive bit reset backup, how will last saturday differential data replace all the data, as incremental backups are run in between the full backup and differential backup.

    Thanks,

    Israel G J

  • pkh's avatar
    pkh
    Moderator
    13 years ago

    will the last differentail data holds all the data modified from the last full backup even if  incremental backups are also involved in the middle.

    No.  The differential backup will only contain files modified since the last incremental backup or full backup. Incremental and full backups resets the archive bit.

    So in your case, if you need to restore something in the middle of the second week, you would need to restore the full backup plus the first week's incremental followed by the latest differential.

    It is a bad idea to mix differential and incremental backups because it can get confusing and confusion is the last thing you want when your server is down.  It is better to stick to a simple scheme like full + incremental or full + differential.  Better yet, just do full backups every time if your backup window permits.  Doing just full backups means that you only have one backup to restore and it is the fastest amongst all the methods.

    All the above is applicable regardless of whether you are using the modified time or archive bit methods.

  • gjisrael1420's avatar
    gjisrael1420
    Level 3
    13 years ago

    Thanks for the valuable suggestion. And i was expecting this answer.

    Regards,

    Israel

  • Ken_Putnam's avatar
    Ken_Putnam
    Level 6
    13 years ago

    So in your case, if you need to restore something in the middle of the second week, you would need to restore the full backup plus the first week's incremental followed by the latest differential.

    Shouldn't that be

    Restore Last FULL (monthly), each subsequent DIFF (weekly) & INCR(Daily)  in chronological order??

    (the weekly DIFF is really only an INCR, since each INCR resets the archive bit every night)

  • robnicholson's avatar
    robnicholson
    Level 6
    13 years ago

    Backup Exec's restore method is my #1 pet hate with the product (closely followed by the meaningless always-reference-tape error messages).

    With deduplication, it would make sense to do a full backup once a month and then a whole series of incremental backups.

    Except if somebody asked you to restore a folder on the last day of the month which means you going through up to 30 paths drilling down A LONG WAY to the SAME FOLDER just in case a file was modified in the folder on each day.

    It's possible this is what synthetic backups are all about but all I want is to say "Restore me this folder as it was on the 30th August".

    Rob.

  • Old_Timer's avatar
    Old_Timer
    Level 2
    2 years ago

    What I've found works best is to do a monthly FULL, weekly INCR and daily DIFFs. That way the number of restore sets is limited, the worst case being 1 Full + 4 Incr + 1 Diff. It took me a while to come to this, but it has served me well. I've not seen it proposed elsewhere, but that doesn't mean it's wrong! I agree the BE methodology is confusing to start with, but after 20 years it gets easier! :grinning_face: