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Thread: backup to disk, without tapes/vtapes

  1. #1

    Question backup to disk, without tapes/vtapes

    Hi all,

    We don't have tapes, and would thus like Amanda to backup on disk (e.g. an external USB disk). Let's say we have one 100 GB disk for the backups, and also assume that this is always enough for one full backup, plus 30 days worth of incremental backups. What is the best way to configure Amanda to be able to use this disk (and have at least 30 days worth of backups)?

    As far as I understand the only way if you don't have tapes, is to use virtual tapes. How many vtapes should I create, and of what size?

    I assume at least 30 (since I would like to have backups of 30 days). If we create 30 vtapes, of 3 GB each, we should also use tape_splitsize to split dumps across tapes, since the full backup is larger than 3 GB. But then the full backup will use >1 vtapes, say 20, which would leave us with 10 vtapes. Since Amanda does not append to tapes, the remaining 10 vtapes are not enough for 30 days worth of incremental backups.

    Should I use 30 vtapes of 100 GB each, with no holding disk?

    Another option would be to use a holding disk of 100 GB (ie. the whole disk), and make it never try to flush to tape. To do this we can configure only one large vtape, say 1 TeraB, and configure the holding disk to flush when it accumulates 10 tapes worth of data (which it never will), and set reserve=0 (to not degrade backups). In this case how can we specify that we only want the last 30 days worth of backups (i.e. day 31 overwrite day's 1 backup, instead of just appending to the holding disk)?

    What would you suggest? Shouldn't there be an easier way to just tell Amanda to not use tapes/vtapes at all?

    Thanks,
    Yannis

  2. #2
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    Quote Originally Posted by imavroid View Post
    Hi all,

    We don't have tapes, and would thus like Amanda to backup on disk (e.g. an external USB disk). Let's say we have one 100 GB disk for the backups, and also assume that this is always enough for one full backup, plus 30 days worth of incremental backups. What is the best way to configure Amanda to be able to use this disk (and have at least 30 days worth of backups)?
    Given this scenario, I would set up 30 tapes of the size that is big enough for a full backup of your single, largest backup entry. 30 times the size of this tape may be more than 100G but this doesn't matter as long as you know that one full backup of all your entries plus 30 days of incrementals will fit in your amount of disk space (and, of course, while keeping an eye on it). With this, you won't need to split things across tapes. When you start making your first runs, Amanda will need to get a full backup of every entry and will make as many full backups as it can to each nightly tape until, after enough runs, all entries have been backed up in full. After this, Amanda will be mostly making incrementals for awhile yet will start making the best mix of fulls and incrementals over time to spread things out as nicely as possible over the monthly period.

    Another option would be to use a holding disk of 100 GB (ie. the whole disk), and make it never try to flush to tape. To do this we can configure only one large vtape, say 1 TeraB, and configure the holding disk to flush when it accumulates 10 tapes worth of data (which it never will), and set reserve=0 (to not degrade backups). In this case how can we specify that we only want the last 30 days worth of backups (i.e. day 31 overwrite day's 1 backup, instead of just appending to the holding disk)?
    If you regularly run
    Code:
    amadamin <config> holding delete
    the only data that will be kept on holding disk are incrementals since the previous full backup. If full backups are made every 30 days, then you will in essence not have more than the last 30 days worth of incrementals on holding disk.

    If you only have 1 enormous tape, all full backups will have to be made on the same run, however. If this is not a problem for you, then this could be a good plan. You could do something similar except with using a few big tapes instead of just one to spread things out more over time.

    What would you suggest? Shouldn't there be an easier way to just tell Amanda to not use tapes/vtapes at all?
    It would be a nice option yet, I imagine as Amanda started when tapes were the most practical media for backup, it is a long way from where it started. Nonetheless, I'm sure it has and will continue to be considered.

    Paul

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