Skip to main content
NetApp Knowledge Base

NDMP backups to fibre channel tape exhibit sporadic low throughput

Views:
1,521
Visibility:
Public
Votes:
2
Category:
ndmp
Specialty:
dp
Last Updated:

Applies to

  • Two or more ONTAP cluster nodes, with each node connected to fibre channel tape.
  • NDMP is running in SVM-scope mode.
  • Data Management Application (DMA) configuration contains all nodes' tape device paths.
  • DMA is not configured to prefer local device paths, but will instead use any available tape device to complete a backup or restore.

Issue

  • NDMP backup or restore takes longer than usual.
  • Compared to previous jobs, the "slow" job exhibits lower throughput.
  • The low throughput is sporadic -- The same job will run at acceptable throughput during one attempt, and then exhibit low throughput on another attempt.
  • All backups, both fast and slow jobs, are being written to SAN tape devices connected to the NetApp cluster nodes.

A "dump to null" test of the volume associated with the slow job does not indicate a read throughput bottleneck.

Example:

The volume "data1" on SVM "nasdata" usually backs up at a rate of ~200 MB/sec, but will occasionally back up at ~75 MB/sec.

If the backup log is examined, the jobs that run at higher throughput have b=60 in the dump options:

dmp Sat May 11 17:10:50 IDT 2019 /nasdata/data1(3) Start (Level 0, NDMP:96285)
dmp Sat May 11 17:10:50 IDT 2019 /nasdata/data1(3) Options (b=60, u)

The jobs that run at lower throughput have b=0 in the dump options, as well as TCP receive and send buffer sizes:

dmp Sat May 11 01:49:54 IDT 2019 /nasdata/data1(7) Start (Level 0, NDMP:36047)
dmp Sat May 11 01:49:54 IDT 2019 /nasdata/data1(7) Options (b=0, u, TCP recv buffer size = 33580, TCP send buffer size = 33580) 

 

Sign in to view the entire content of this KB article.

New to NetApp?

Learn more about our award-winning Support

NetApp provides no representations or warranties regarding the accuracy or reliability or serviceability of any information or recommendations provided in this publication or with respect to any results that may be obtained by the use of the information or observance of any recommendations provided herein. The information in this document is distributed AS IS and the use of this information or the implementation of any recommendations or techniques herein is a customer's responsibility and depends on the customer's ability to evaluate and integrate them into the customer's operational environment. This document and the information contained herein may be used solely in connection with the NetApp products discussed in this document.