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Thread: Amanda suitable for us? Planing Backup System

  1. #1
    Join Date
    Feb 2012

    Default Amanda suitable for us? Planing Backup System


    I am working in an university workgroup and doing the computer administration. At the moment we have a NAS at the University Server Farm with 2Tb space. On this NAS we have the very important files. The university backs up this 2tb every day and keeps the backup for 5 days. Normaly this is enough, but we had the problems that somebody changend some files and corrupted them and after a few days this corruption was discovered but we did not have a suitable backup because the 5 days where gone.

    So to prevent this my professor wants a local backupsystem for the workgroup backing up the NAS and keeping the data for a few more days. Additionally he wants to backup some of the pcs in the workgroup like his own one. As always as cheap as possible. So no tape system.. but data should be stored for 10 years..

    So at the moment I am planing this backup system. i want to run 2 seperated raid 1 systems on the maschine. one backing up the workgroup data. Here is the first question. Is it possible to backup the OS like with windows home server and reinstall the OS from the amanda backup server?

    Second i planned another raid 1 for the NAS with 2*3tb. And here is the main problem for me. I want to perform a full backup of the NAS every half a year or so and then backing up only the changed files every day but i want to have a backup history.. so keeping the backup of the changed file instead of overwriting it. For example File 1 is backupped, file 1 is changed and backupped again and i have File1 and File1_changed. Is this possible with amanda?

    Thanks for your help.


  2. #2
    Join Date
    Sep 2007


    The perennial question about doing backups for large amounts of data over long periods of time while spending very little money. The simple answer is that yes, Amanda can do the job, but you should spend some money on hardware. You can calculate some requirements fairly easily. Others are things that are learned from experience.

    Large drives are becoming more common. Cheap large drives are likely to fail earlier than you would like. Raid 5 is insufficient to cover the risks, in part because of rebuild stress when a single drive fails and is replaced, in part because of the comparable dates of a batch of drives. What you really want are enterprise quality drives that cost more, and you want Raid 6. We've been recently getting Supermicro servers with eight 2T drives. Configure 2 of them for various things like Amanda holding disk, swap, and mirrored boot partitions. Configure 6 of them Raid 6. That gives you just under 8T for data. The drives we bought most recently have 5 year warranties. Not cheap, but substantially less expensive than the Sun/Oracle gear we have bought in the past. We're using Ubuntu LTS server now.

    If you are planning for 10 years, you have to plan for data migration when you replace systems, and you have to plan for the sysadmin expertise to monitor and maintain systems. It doesn't do you much good to have Raid 6 if no one notices when a drive fails.

    Calculations -- how much data do you have? Is that 2TB all your data? Or is that shared space? A full backup is going to take that much space. The size of incremental backups will depend on how much you are adding or changing. Try to put some numbers on it. Then lay out a sequence of full and incremental backups and calculate how much storage it is going to require. Assume that is conservative. If you assume the University is covering you for 5 days, maybe you can run backups twice a week.

    The policy we have taken on backup and recovery is that we back up data, not systems. On failure, re-install the system and then recover the data. For Ubuntu servers, this means grabbing /etc so that we have configuration data, perhaps /var/log for logs, and then /home and /data. For PCs, users are told to save important things to a share on the server, which will then be backed up. Otherwise, Mac and Windows machines eat a lot of back up space with OS and applications, which aren't really needed, because it is so easy to just re-install. Data management by users is an important issue. If they have a handle on that, it makes backups easier.

    Finally, there is the issue of backup cycles. Running only one full in 6 months and then 6 months worth of daily incremental backups would be a nightmare for tracking and for recovery. For starters in understanding Amanda backups, you should read over [url] nda_use_them%3F[/url]. You want to come up with a logical way of breaking down the data stored on the University NAS into a reasonable number of Disk List Entries (DLEs). Then come up with a dump cycle that will allow the full backups to be spread out so that they are managable. Without an endless stream of tapes, I don't think you will find it possible to keep all your backups for years on end. Just like the University has a 5 day window, you will have to choose your own window. It might be 6 months, or it might be less. The risk is that someone will delete a file, forget about it, and then a year later decide they need it. Even the classic example where monthly full backup tapes are kept indefinitely will miss the file that was created on the 10th of the month, accidentally deleted on the 25th, and not noticed until 6 months later. It's gone.

    So, the bottom line is that without a lot of money, and maybe keeping daily tapes forever (constantly buying new tapes), even backups can't save you if you don't manage data in a reasonably intelligent fashion. However, if you manage your data, then backups with a reasonable cycle, covering you for maybe 6 months, should be sufficient to cover hardware failures, mental slips, etc. You do want to have at least a few full backups at any given time. You don't want to rely on a single full backup, or even on just 2. I typically have a dump cycle of a week, with a full backup of each DLE, and keep them for a tape cycle of 6 to 10 weeks.

    I hope that at least provides some food for thought.

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