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I'm looking to run a series of Symantec BackupExec 2010 backups to a network share hosted on a NAS device. The goal is to keep two weeks of backups consisting of a weekly full and daily incrementals.

  • How should I arrange the B2D folders?
  • What should the maximum B2D file size be?
  • For the media set, what should the overwrite protection and append periods be to accomplish this?

Note: The NAS storage doesn't have any limitations on file size.

Edit: I have tape rotation working well here. I had B2D running for the past few weeks using 4GB file sizes and a 2 week retention period. I've run into problems in recent backups because the jobs would stall, waiting for appendable media. I could not determine if there was some mismatch in the append and overwrite periods. At what point does the B2D image continue expanding versus overwriting previous files?

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up vote 2 down vote accepted

You don't specify what filesystem the NAS is actually running, so this advice is assuming you're running NTFS.

When creating a backup-to-disk directory structure the following are a good idea:

  • The block-size the volume was formatted with should be large. NTFS defaults to 4K which is way too small. 64K would be entirely appropriate for a B2D volume.
    • Block/logical-sector alignment can improve performance, though you may not feel up to futzing with this.
  • If possible, arrange things so only one volume is being written to at any given time. This increases the sequentialness of your backup files in the filesystem, and thus improves performance.
  • If using NTFS, massive files (100GB) are harder on the OS than lots of smaller (10G) files are.

When we were still with 10D it did seem that BackupExec re-used existing backup-files in preference to spinning up new ones. This is fairly smart in that once a file is laid down, if it was done in one segment it'll stay that way so the volume won't fragment nearly as much as delete/recreate would. It depends on your storage, but usually keeping those files contiguous will noticeably improve your read/write performance.

For append/protection periods, it is my understanding that the Append period starts the moment the media is written to the first time and the Protect period resets every time it is written to. So if a file is written to on 1/5 with a 7 day append period and a 14 day protection period, the append period will end on 1/12 but the overwrite-protection period may not end until 1/26.

Variability in how fast your backups run will cause media to stagger their protection periods. If a backup stalls over a weekend and resumes Monday after you kick things, that media will come overwriteable 2 days later than normal and that can cause you problems later on down the road. Plan for extra space in your B2D archives for this kind of thing.

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The NAS is really a CIFS export from a NexentaStor system (OpenSolaris). The zvol is large and consists of a 3 x 3-disk raidz stripe using 1TB drives, so space is not an issue. You're right about the timing, and I needed a better understanding of when the append and overwrite counters began. I was using 4GB file sizes, butI can probably safely increase that size. – ewwhite Jan 26 '11 at 17:25

A little reading of the BackupExec Admin guide seems in order here.

•How should I arrange the B2D folders?

However you want them arranged. We can't answer this for you.

•What should the maximum B2D file size be?

Whatever you want the maximum size to be. Use the B2D wizard and accept the default settings.

•For the media set, what should the overwrite protection and append periods be to accomplish this?

Whatever they need to be to meet your media retention goals/needs.

Your question is somewhat of the Backup 101 nature. A little reading/research on your part will go a long way to a better understanding of backups and how to configure them to meet your needs/goals.

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See additional information above. – ewwhite Jan 26 '11 at 16:09

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