NetWorker: vProxy Performance mode cloning loses optimization with Retention Lock devices

Summary: This article describes a bug which involves a flaw in the implementation of NetWorker's VMware vProxy backups when used with Data Domain Retention Lock devices.

This article applies to This article does not apply to This article is not tied to any specific product. Not all product versions are identified in this article.
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Symptoms

  • Backup or cloning may appear slower than expected for NetWorker VMware Protection (NVP) vProxy savesets on Retention Lock devices
  • Error appears in ddfs.info log despite apparent success of backup or clone job:
Attempt to rename non-empty directory /data/col1/mtree/device/active/abc3b7ed-00000006-fd27be29-6627be29-00045000-595e3c56
dboost-<nsrsvr.demo.local-55146>: ddboost_api ERROR: ddp_rename() failed, FromPath //mtree/device/active/abc3b7ed-00000006-fd27be29-6627be29-00045000-595e3c56, ToPath //mtree/device/21/06/abc3b7ed-00000006-fd27be29-6627be29-00045000-595e3c56,  Err: 5034-nfs rename failed (nfs: Permission denied)

Cause

The problem results from an undiscovered flaw in implementation. Since Data Domain Retention-locked devices do not allow renaming of non-empty directories, part of NetWorker's normal backup and clone workflow silently fails, falling back to a different mechanism which prevents optimization success.

Resolution

The workflow is corrected in upcoming NetWorker versions:
  • 19.10.0.5
  • 19.11.0.2
  • 19.12+
The problem does not appear to affect Capacity Mode. Switching to Capacity Mode as a workaround may alleviate the problem in the short-term, but upgrade will be recommended.
 
NOTE: Changing from one backup optimization mode to another (for example, from Optimized for Performance to Optimized for Capacity) requires performing a new full level-zero backup as the starting point for subsequent backups. Ensure that the Data Domain device has sufficient capacity. Since backups for each optimization mode must co-exist during this period, backups consume twice the usual storage capacity until the last Optimized for Capacity backup expires, as defined by the retention period. After this, storage consumption will return to normal.

Additional Information

NetWorker supports two types of backup optimization modes for vProxy backup to Data Domain systems—Optimized for Capacity, and Optimized for Performance. You can apply the optimization mode to vProxy protection groups during backup. The Optimized for Capacity mode uses variable size segmentation, which produces more overhead in data processing due to the higher deduplication rate, but reduces the capacity consumed on the Data Domain system. Optimized for Performance provides performance improvements during incremental back ups of virtual machines using Changed Block Tracking (CBT) and replicates data to a Data Domain system, and is effective when backing up large VMDK files. Although Optimized for Performance results in additional space use on the Data Domain device (around 20%), this mode significantly improves random I/O performance for instant access restores.

Affected Products

NetWorker
Article Properties
Article Number: 000225863
Article Type: Solution
Last Modified: 12 Sept 2024
Version:  2
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