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Monitor Filesystem IO Calls for Messaging Server (Doc ID 1351483.1)

Last updated on APRIL 21, 2021

Applies to:

Oracle Communications Messaging Server - Version 6.0.0 and later
Information in this document applies to any platform.


Email is an I/O-intensive application. It is not just the throughput in terms of the amount of data -- because the IO operations tend to be relatively small (in terms of what modern IO systems are capable of) -- but the rate of operations (also called IOPS -- IO Operations Per Second). Therefore most email performance problems tend to be due to disk I/O bottlenecks.

There are tools to monitor disk I/O performance (such as the asvc_t column in iostat -xpn), but sometimes the bottleneck is in the filesystem rather than the lower level storage devices.

This article provides a DTrace script to monitor a few of the disk-IO-related syscalls used by some of the Messaging Server processes. This should be a basis for deciding whether your problem is related to the file system or disks storage or something else.

Also refer to:

Troubleshooting Steps

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In this Document
Troubleshooting Steps
 A caveat on the imap-txns-cmds-IO.d script
 The script
 Running the script
 Example output
 Summary of filesystem type and syscalls by process
 Details of timing of filesystem type and syscalls across all processes
 What to do about it
 More detail
 IO by IMAP Command
 Top Write-IO users/folders
 Performance impact of delivery-perf-user.d
 iotop command on Linux
 iotop DTrace on Solaris

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