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|Info about known problems|
|<< Frequetly Asked Questions|
|Slow down of download speed with IISTracer|
We have been using IISTracer (company license) on IIS6, Windows Server 2003 (fully patched) and are very satisfied with it. There is however one big minor disadvantage I just found out. When doing network tests on a 100MB.BIN file, I download with 800kb/sec with IISTracer enabled. As soon as I disable IISTracer (remove from ISAPI filters) my download speeds up to 3000kb/sec. I've tested this from multiple locations.
Is there any reason for this slowdown, and is there any way I can prevent this from happening? A slight decrease in performance would be ok, but this is simply too much.
This problem is with monitoring of SEND_RAW_DATA event. IIS has a strong performance overhead on the SEND_RAW_DATA notification. Please switch-off the notification in monitoring (configuration - Monitored events - SEND_RAW_DATA). You have to restart IIS to apply changes.
IIS Tracer web site monitoring tool from 2.8.0 version has a new option - monitor only first SEND_RAW_DATA request event. So you can see that the request is in SEND_RAW_DATA state. You cannot see a download progress of the request with the option.
|IIS crash with IISTracer + other special filters|
This problem was solved with 1.01 version of IISTracer.
IIS Tracer web site monitoring tool cannot work on some versions of IIS with filters, which has one special construction - the filter uses pfc->WriteClient( pfc, Data, &dataLen, 0 ) in SF_NOTIFY_SEND_RAW_DATA event. There is no error (unhandled exception) in IIS Tracer web site monitoring tool, there may be no error in such other filter, but IIS crashes if IIS Tracer web site monitoring tool and such filter are both running in the IIS server.
We have found two problematic IIS filters till now
- our EnhancedLog (which was written for IIS 1.0)
- frontpage extension ISAPI filter.
We have switch off monitoring of SF_NOTIFY_SEND_RAW_DATA IIS event in default configuration.
See IIS ISAPI notifications description + Summary of IIS Event Ordering