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DPM backup terminologies RRS feed

  • Question

  • Hi

    As during synchronization freq as well as during express full backup, DPM creates recovery points (from which we can restore the data) and both are incremental backups then why to run two separate backups (synchronization freq & express full backup)?

    Please help me to understand.

    Tuesday, February 11, 2014 8:15 AM

All replies

  • I'll take a simple exemple.

    During SQL Synchronization Point (in case of a Full Recovery Model database), DPM will get the logs.

    During the Express Full for the same database DPM will transfer changed blocks.

    Tuesday, February 11, 2014 8:49 AM
  • Hi,

    To be able to understand this correctly you will have to look at each type of application data.

    As an example, if we intend to backup Exchange we utilize the Exchange VSS Writer. For each synchronization and express full backups we create a recovery point. We can then recover data from both synchronizations and express full backups.

    If we compare it to an SQL with simple recovery model, we only create a recovery point for each express full backup. We can then only recover data from express full backups.

    If we instead compare it to an SQL with transaction logs, we create a recovery point for each synchronization and express full backup. We can then recover data form both synchronizations and express full backups.

    Better explained at:
    http://technet.microsoft.com/en-us/library/bb808837.aspx

    File Data backups on the other hand is only made up from synchronizations and recovery points. We can only recover data from recovery points.

    So why do we run frequent synchronizations between each recovery point for File Data backups?

    1) Instead of transferring a huge chunk of data right before the recovery point is made we transfer small chunks over the course of the day.

    2) Even though we cannot recover data from a synchronization immediately for file servers, we are able to do a manual recovery point making the data available for recovery. So if we sync every 15 minutes, we have a data loss window of 15 minutes, compare it to an 6 hour window if we run a synch every 6 hours.

    So why do we not create a recovery point for each synch for file data?
    The limitation is the Windows VSS Infrastructure, it only supports 64 snapshots.
    As an example, if we take 2 recovery points each day, we can only keep data for 30 days on disk.

    I hope that helps you to understand it a bit better.

    Kind regards,
    Tobias


    Tuesday, February 11, 2014 9:10 AM
  • So you mean to say after SQL synchronization we will not restore the data? Please clear.
    Thursday, February 13, 2014 11:32 AM
  • Quote from http://technet.microsoft.com/en-us/library/bb808837.aspx:

    "SQL Server databases that are log-shipped, in read-only mode, or that use the simple recovery model do not support incremental backup. Recovery points are created for each express full backup only.

    For all other SQL Server databases, synchronization transfers a transaction log backup, and recovery points are created for each incremental synchronization and express full backup. The transaction log is a serial record of all the transactions that have been performed against the database since the transaction log was last backed up."

    So the answer is different depending on how SQL is setup.
    In the first case we can only directly recover from express full backups since we only create recovery points from those.

    In the second case we can directly recover from both synchronizations and express full backups since we create recovery points from both.

    I hope that clears the confusion.

    Thursday, February 13, 2014 12:33 PM

  • For File Protection, synchcronization brings across the changed blocks in
    files to the DPM server. However recoveries can only be performed from
    shadow copies on the DPM server (recovery point). Synchronizations can run
    every 15 min, but recovery point creations run less often (default thrice a
    day).

    For Application Protection, every incremental is recoverable so every 15 min
    point in time is recoverable.


    Applications refer to things like SQL and Exchange.  Like standard file server data, these applications can synchronize at whatever interval you specify.  The difference is that basic files can be restored from each and every synchronization (recovery point = each time it's synchronized).

    But for applications, it can depend on what the application itself support.  If the application supports incremental backups, then you can get recovery points for each synchronization - if it doesn't, then although the data synchronizes on your interval, you will only get restorable recovery points for an "express full" backup which is created at the interval you specify in the lower part of the window.  Synchronizing at a regular interval throughout the day is still helpful, though, because it prevents a huge resource/bandwidth drain at the express full time slot because most of the data will already be synchronized...

    http://setspn.blogspot.ru/2011/12/scdpm-backup-sql-and-truncate-sql-logs.html

    Have a nice day !!!


    Friday, February 14, 2014 7:32 AM
    Moderator