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Solving Backup problems with DPM

08/07/2011

I get many questions about the functioning of DPM after having posted the videos of the product (http://bit.ly/rh35b6).

Many issues are related to the use of tapes and robots, so I edited the post about using tape for mes past (http://bit.ly/ouqp6O) and I will now address other very common errors and how to fix them.

Error with Volume Shadow Services (VSS)

The DPM process is not carried out directly on the data and Yes from the snapshot data using VSS, which is known by the Shadow Copy.

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Thus, most problems with backups are VSS-related that you cannot generate the necessary data for DPM.

The first and most easy way to resolve is to manually create a restore point full, which creates the snapshot again on server backup source, and generally resolves the problem when the VSS database is corrupted.

The second way to solve the problem is CHKDSK run a on the source disk backup, because the VSS writes data in unallocated space on disk and the checkdisk makes the check for problems in areas not allocated (free space).

The third way of solving the problem is to go to the properties of the Shadow Copy of the disk (open the Explorer as an administrator and right-click) and verify that the properties are correct. Verify that the Shadow is occurring on the disks by allocated size and enter the properties and make sure there is space available. Note that the Shadow Copy need not Enabledbe, because this is another feature.

The fourth way to solve the problem is using VSADMIN tool and use the commands from the list of resources. If any of the error lists the ideal is to delete all shadows with the parameters VSSADMIN DELETE. With this action will restart the VSS on all disks in the next backup. However it is important that at the first attempt occurs error, because the shadow will reboot. If this occurs, wait a few minutes and try again.

The fifth and final way to resolve problems is to check for available updates and hotfix to the server data source, and also of DPM itself that is in the QFE (http://www.microsoft.com/download/en/details.aspx?id=209532).

Specific problems with Hyper-V Protection

One of the great advantages of DPM is to back up virtual machines (VMs) directly from the service of Hyper-V, which is much faster to copy and restore to include the entire VHD backup.

However, in this case it is necessary to take various precautions.

The first one has to do with DAS (Direct Attach SCSI), whether on a local disk or sotrage If DPM is in Hyper-V host, which I never recommend by signal.

In this case, DPM will occupy the entire band of storage for backup and Hyper-V will overthrow the service by understanding that the VHD became unavailable. If you have cluster, the cluster service will drop by indicate simultaneous access on the same disk. Therefore, do not use DPM physically connected on the same controller that is Hyper-V.

Another problem is the Hyper-V to understand that there were concurrent enrollment program access to the same data (VHD) and in this case apply the KB 2545685 (http://support.microsoft.com/default.aspx?scid=kb;en-US;2545685) that resolves the problem.

If your Hyper-V environment is based on the cluster may also be necessary if the KB above does not resolve to perform the tasks described in http://technet.microsoft.com/en-us/library/ff634192.aspx document that serves to influence the way the snapshots are generated when your hardware does not support this operation.

Finally, follow the steps http://technet.microsoft.com/en-us/library/ff634205.aspx document disabling protocol chimney or enabling auto mounting of volumes to the VSS.

Conclusion

Backup systems are easy to implement but require high knowledge of the environment to be managed, since a great deal of local resources such as VSS and CSV in the case of clustered Hyper-V are not so simple to be controlled.

However, with the tips above managed to fix the problems I had at various clients with success!

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