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Chris_C1's avatar
Chris_C1
Level 2
15 years ago
Solved

Purpose of nodata storage checkpoints.

 

I am confused about the purpose of the "nodata" checkpoint type in VxFS.

 

I understand the normal full data checkpoint, but can somebody explain

why you would want to use the "nodata" version?  I understand that you

can see the file structure, but if you can't get file data what is the

point?  what am I missing?

thanks!

Chris

  • NetBackup creates no-data checkpoints automatically as part of BLIB.

    So, there is no reason you, as an end-user, should ever create a no-data checkpoint.

  • Hello Chris,

    I am not well expert in checkpoints but I believe nodata checkpoints would be the fastest ones to recover in occurance of metadata corruption of a filesystem.

    There are scenario's where filesystem metadata was corrupted (but the entire data exist ), in short the map or index of data is corrupted /missing. For e.g if you were upgrading a filesystem version which got hung or process was incomplete causing in corruption. In such cases you can simply get your metadata back by a nodata storage checkpoint.

    one more thing that strikes to my mind, what if you want to verify the integrity of a production filesystem which is mounted ? well we can use the nodata checkpoint to mount to a temporary mount point & very well run a fsck on that & can see the consistency or integrity.

     

    Gaurav

  •  

    Gaurav, the first scenario is interesting(ie: using the nodata

    checkpoint to recover the structure). However the second

    scenario  is not possible: you cannot fsck a storage checkpoint.

     

    There has to be something more substantiasl to the "nodata" cheeckpoints but I

    am just not seeing it.

     

    Chris

  • Hi Chris,

    Nodata storage checkpoints keeps track of changed blocks only without copying the

    actual data. This is used for Block level incremental backup's which works under the

    filesystem layout. It uses the volume devices to take backup. Netbackup has this

    feature and utilizes this nodata storage checkpoint to track the changed blocks

    on the filesystem.

     

    Hope this clarifies your question. Let me know if you need more details on BLIB feature.

     

    Regards

    Srini

  • NetBackup creates no-data checkpoints automatically as part of BLIB.

    So, there is no reason you, as an end-user, should ever create a no-data checkpoint.