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Knowledge Base

A RHEL 5 Inherent Defect Causes a Performance Fluctuation of a LUN

Publication Date:  2013-06-19  |   Views:  334  |   Downloads:  1  |   Author:  z00444668  |   Document ID:  EKB1000029974


Issue Description

Product and version information:
  • T series storage products
  • The operating system of the application server is Linux rhel5u3_x86-64 2.6.18-128.el5.
  • The HBA is ATTO-FC82EN.
  • The Fibre Channel switch is Brocade 5100.
  • The storage device and application server use the Fibre Channel switch network, as shown in the following figure.

    When small data blocks (less than 16 KB) of the storage device are read and written on the application server, the performance fluctuation reaches 18% to 20%.

Alarm Information


Handling Process

Contact Red Hat technical support engineer for assistance.

Root Cause

The same test is executed on a peer vendor's storage device and the same symptom occurs.
It is concluded that the significant storage performance fluctuation is due to the incompatibility between the Linux rhel5u3_x86-64 2.6.18-128.el5 operating system and ATTO-FC82EN HBA.


The storage performance fluctuates when the rhel5u3_x86-64 2.6.18 operating system and the ATTO-FC82EN HBA are both used in a SAN network environment. Performance-demanding small data block services do not fit in such an environment.