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42619:nsrndmp_recover: NDMP Service Error: Unable to perform a single file restore on a deduplicated file. Perform a full VBB restore on a separate file system and copy the deduplicated files that you want.”

March 9, 2012

Celerra NDMP VBB (NVB) file-by-file recovery of deduplicated file system fails.

NDMP File system being backed up with VBB (aka NVB) is deduplicated using Celerra native Deduplication, while recovering those NDMP backup data using file-by-file recovery method, file names restored but files contain 0 bytes. Recovery fails with the error message:

“42619:nsrndmp_recover: NDMP Service Error: Unable to perform a single file restore on a deduplicated file. Perform a full VBB restore on a separate file system and copy the deduplicated files that you want.”

NDMP Volume backup (NVB) “which also referred to as Volume Based Backup (VBB)” can backup up Celerra Data Deduplication-enabled file systems and restore them in full by using the full destructive restore method, Because NVB operates at the block level (while preserving the history of the files it backs up), it does not cause any data reduplication when backing up a deduplicated file system. The data in the file system is backed up in its reduced form. This means that the benefits of the storage efficiency realized in the production file system flow through to backups.

However, Celerra does not support a single-file or file-by-file restore of deduplicated files from NVB backups. Hence, EMC recommends that NVB backups of deduplicated file systems should be used as part of a strategy where a single-file or file-by-file restore is done from locally or remotely replicated SnapSure checkpoints and not from tape. Because the majority of file restores happen within the first few days after their deletion, a SnapSure checkpoint is an efficient and faster way to restore most files.

The only possible way to recover Celerra VBB (NVB) backups of a deduplicated file system is to perform a Celerra Full Destructive Restore (FDR) which requires a complete save set recovery into a raw volume. The original file system of which the backup was done must be converted into a raw volume “which will destroy the production file system”, OR, another raw volume of equal or larger size must exist or be created on the Celerra to direct the save set recovery into.

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One Comment
  1. Stephan permalink

    The full destructive restore does not necessarily need to go to the original “production file system”.

    If enough space is available on the system a raw file system of the same size can be created and used for the restore.

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