PowerScale: NDMP Snapshot Fast Incremental taking longer than expected

Summary: Under certain conditions, NDMP may experience performance issues when attempting to run Snapshot faster incremental jobs.

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.
Check out other resources

Instructions

Understanding SNAPSHOT Mode

In SNAPSHOT mode, after receiving the NDMP_DATA_START_BACKUP with variables from the Data Management Application (DMA), PowerScale creates a new snapshot and uses the supplied BASE_DATE variable to find the associated snapshot. This snapshot is used to create the Change Database (cdb) between the two snapshots. The Change Database (cdb) is tracked by seconds, and the time it takes to build depends on the number of changes made since the last backup for the FS.

 

Impact of High Change Rates on NDMP Performance

When the change rate exceeds 2% for the path associated to the backup, NDMP performance can be impacted due to the large number of changes and the time it takes to build the Change Database (cdb).

 

Troubleshooting: Checking Backup Mode and Change Database (cdb) Build Time.

 

To determine if jobs are running in SNAPSHOT FI mode, use the following commands:

  • Live: grep BACKUP_MODE /ifs/.ifsvar/modules/ndmp/node*-ndmp.trace |less
  • Logs: grep BACKUP_MODE local/ifsvar_modules.tar/modules/ndmp/trace/node*-ndmpd.trace |less

 

Output may look similar to:

local/ifsvar_modules.tar/modules/ndmp/trace/node13-ndmpd.trace.9:               Name (value) : BACKUP_MODE (SNAPSHOT)
local/ifsvar_modules.tar/modules/ndmp/trace/node13-ndmpd.trace.9:               Name (value) : BACKUP_MODE (SNAPSHOT)
local/ifsvar_modules.tar/modules/ndmp/trace/node13-ndmpd.trace.9:               Name (value) : BACKUP_MODE (SNAPSHOT)
local/ifsvar_modules.tar/modules/ndmp/trace/node13-ndmpd.trace.9:               Name (value) : BACKUP_MODE (SNAPSHOT)

 

To verify the amount of time spent building the Change Database (cdb), use the following commands:

  • Live: grep cdb /ifs/.ifsvar/modules/ndmp/node*-ndmp.trace | less
  • Logs: grep cdb local/ifsvar_modules.tar/modules/ndmp/trace/node*-ndmpd.trace | less

 

Output may look similar to:

Log  :  CPU  user=3986.358010  sys=380527.011168  ft=244728.838385  cdb=76561.738506
Log  :  CPU  user=412.115524    sys=98946.219716   ft=14675.093316     cdb=8817.705529
Log  :  CPU  user=1971.577102  sys=380480.629420  ft=116.502309        cdb=93954.847617
Log  :  CPU  user=1768.215238  sys=380712.643814  ft=36.631554          cdb=73611.565402

 

Recommended Action

If NDMP performance impact is found to be related to the time spent building the Change Database (cdb), for better performance consider revising the BACKUP_MODE to TIMESTAMP for better performance.

 

For more information about SNAPSHOT mode and TIMESTAMP mode, refer to KB PowerScale (Isilon) OneFS 9 - NDMP Timestamp Backup Mode vs. Snapshot Backup Mode job types and requirements

 

Affected Products

PowerScale OneFS
Article Properties
Article Number: 000369783
Article Type: How To
Last Modified: 08 Dec 2025
Version:  2
Find answers to your questions from other Dell users
Support Services
Check if your device is covered by Support Services.