Forum Discussion

TuxanForLife's avatar
11 years ago

Status 129 [DSSU Full] - Can I restore data from an incomplete backup?

Summary :
I have done a Full backup to DSSU, but the DSSU filled up before the backup was complete - I got a status 129.
Will fragments of an incomplete backup be written to tape? Can I restore data from those fragments?

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Details:

I see log entries similar to the following during the backup :
''begin writing backup id HOSTNAME_1372456801, copy 1, fragment 43, destination path /dssu' '2013-06-29 06:34:21.000 "
"successfully wrote backup id adsdev-dc-aus_1372456801, copy 1, fragment 42, 8193024 Kbytes at 8224.573 Kbytes/sec "

My DSSU highwater is 1%, so it's supposed to begin writing to tape ASAP, though technically I believe that it writes a file to tape only once the file is fully written to disk. I wrote about 44 of 8G fragments to the DSSU before it filled up. I guess about 345G to 457G. The FS I am concerned with is 41G. Is there a way to try to recover from an incomplete backup?

The fragments are no longer on the DSSU.
I don't backup the DSSU when I backup the media server.


 

  • Making your HWM 1% is definately not a solution - as you have found out!

    You need to collect all relevant documentation and use it as motivation for disk storage request. Network attached storage is also supported.

    More info in NBU Admin Guide I  under this topic:
    Maintaining available disk space on disk storage units 
    as well as High water mark storage unit setting.

4 Replies

  • After more searching

      * Formal Answer: You cannot restore from an incomplete backup. 
        Suspected reason - An incomplete backup is not indexed in the catalog

      * Informal Answer: DSSU files are TAR archives. If you want to mess with it
        It will be difficult. For a successful backup, you could run : 
         master#  bpimagelist   -L  -backupid  HOSTNAME_1372456801 
         to dump info about it. The 'ID: 002512' will tell you it's on tape 2512.
        You may find a log that tells you what tape the backup is on and can use TAR to recover that fragment and TAR to extract from inside the fragment. It's labor-intensive.


     

  • My DSSU highwater is 1%, so it's supposed to begin writing to tape ASAP

    NO!! This is not how DSSU works!

    The whole idea with Disk Backup is to keep backups on disk for quick restores.

    Duplication to tape only happens as per the schedule that you configure in the Storage Unit staging config.

    Again - it is a duplication, not moving the image. So, there will now be 2 copies of the backup. 
    1 for quick restores on disk and 1 on tape for long term retention.

    You need to provide enough disk space for at least 2 full backups.

    Disk cleanup will only be done for images that have been successfully duplicated to tape.

    Please review these 2 TNs: 
    DSSU cleanup behavior: 
    http://www.symantec.com/docs/TECH66149 
    DSSU relocation behavior: http://www.symantec.com/docs/TECH44719 
     

  • > not how DSSU works.
    > need ... enough disk space.

    There's the rub. We cannot use as intended because we don't have enough diskspace. But although it doesn't provide a nearline copy, what it does for us is to buffer writes to tape to compensate for a slow and uneven network - the entire 8GB file is available as fast as the tape can handle it.
    If there's a more correct way to do this (other than fixing our network - which is beyond my power), I'd be happy to implement it.

    Thank you for the Tech Notes links, Marianne.  I read through them, and also the best practices tech note referenced. Someone I respect told me that he didn't think it was worth doing much NBU tuning (we are on 7.5.0.4) since the software (now) has intelligent defaults and improvements take too many attempts / checking results in order to acheive fairly small gains. We are writing 8G fragments to the DSSU, that seems like a good balance of time to write to disk and time to write to tape.
     

  • Making your HWM 1% is definately not a solution - as you have found out!

    You need to collect all relevant documentation and use it as motivation for disk storage request. Network attached storage is also supported.

    More info in NBU Admin Guide I  under this topic:
    Maintaining available disk space on disk storage units 
    as well as High water mark storage unit setting.