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Thread: What are incremental backups based on?

  1. #1

    Default What are incremental backups based on?

    I am trying to play around with amdump to figure out what incremental backups are based on.

    I have 25 vtapes in my tapecycle, my dumpcycle is 4 weeks, and my runspercycle is 20.

    I used the amadmin force command to make a full backup on tape 7.

    I then ran amdump 26 times. The first one put a level 0 backup on tape 7. The next 24 did level 1 backups on tapes 8 to 25 then tapes 1 to 6. The 26th backup did another level 1 backup overwriting the level 0 backup on tape 7.

    The thing I don't understand is why, if my runspercycle is 20, that I get all level 1 backups constantly. I was hoping that this value would set a maximum amount of runs before another level 0 backup is performed.

    The only thing I can gather from this is that level 0 backups are scheduled based solely on the amount time since the last full backup. I just wanted to test to make sure that my level 0 backups would actually happen, and not leave me with all level 1 backups should I leave this system running on its own.

    I guess my question is what is the point of the runspercycle attribute in amanda.conf if it doesn't allow me to get level 0 backups in this manner? Wouldn't the dumpcycle attribute alone be sufficient?

    I've read through the man pages, but I guess I just don't understand the purpose of the runspercycle attribute. Could anyone explain this to me? The more detail the better! Thanks

  2. #2
    Join Date
    Nov 2005
    Location
    Canada
    Posts
    1,049

    Default

    The dumpcycle is 4 weeks, Amanda do a full every 4 weeks.
    You screwed everything by doing more run that what you are configured for.
    The email report have warned you about overwritting your level 0, Why did you ignored it?
    You should have forced a new full since you do too many run for your configuration.

    runspercycle is useful to balance full dump if you have many dles.

  3. #3
    Join Date
    Jan 2007
    Location
    Richland, WA [USA]
    Posts
    78

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    Quote Originally Posted by nickbetcher View Post
    I am trying to play around with amdump to figure out what incremental backups are based on.

    I have 25 vtapes in my tapecycle, my dumpcycle is 4 weeks, and my runspercycle is 20.
    In doing this, you are TELLING Amanda what you are going to do. Amanda is trusting you to tell it the truth - over the course of the next 4 weeks, you will run 20 backups. Assuming you have enough tapes (no multi-tape backups), that works.

    I then ran amdump 26 times. The first one put a level 0 backup on tape 7. The next 24 did level 1 backups on tapes 8 to 25 then tapes 1 to 6. The 26th backup did another level 1 backup overwriting the level 0 backup on tape 7.
    The idea is that the dumpcycle is a real-world time period, so you just ran more backups than you said you were going to in the 4 weeks of your dump cycle. Amanda trusts you to be doing backups as said you would, and since 28 days haven't yet occurred, there's no reason for another full dump.

    The only thing I can gather from this is that level 0 backups are scheduled based solely on the amount time since the last full backup. I just wanted to test to make sure that my level 0 backups would actually happen, and not leave me with all level 1 backups should I leave this system running on its own.
    That's mostly true. The scheduler in Amanda can also "promote" backups of upcoming full backups - I believe that's based on how much room there is on the current tape and what it expects to use, but I haven't looked at how it actually works.

    I guess my question is what is the point of the runspercycle attribute in amanda.conf if it doesn't allow me to get level 0 backups in this manner? Wouldn't the dumpcycle attribute alone be sufficient?
    That info helps Amanda to properly spread full backups of all your systems (DLEs) within your specified environment. If you don't tell Amanda the truth about what you are going to do, it will schedule incorrectly.

    -Andrew (sheepishly admitting to still using Amanda-2.5.2p1 to back up ~ 450 filesystems a day from Linux, Solaris, and IRIX boxen...)

  4. #4

    Default

    So these attributes are used by Amanda only to determine how to spread full backups throughout the dumpcycle?

    If so, then that makes sense to me

    Currently, I am only backing up a single directory on a single host for practice, just trying to get a feel for the way Amanda works. I can see now why this functionality would not be apparent in my testing.

    I have more questions now but I will start a new post instead of putting them on this one!

    Thank you for the expedient quality replies. I am a real newbie at this, but I'd really like to come to a full understanding. It is obviously important that an admin should know exactly how this stuff works

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