ADSM-L

Re: Throughput Magic Calculation

2004-09-07 15:57:27
Subject: Re: Throughput Magic Calculation
From: "Stapleton, Mark" <mark.stapleton AT BERBEE DOT COM>
Date: Tue, 7 Sep 2004 14:57:25 -0500
From: ADSM: Dist Stor Manager [mailto:ADSM-L AT VM.MARIST DOT EDU] On 
Behalf Of Roger Deschner
>If I look at SQL variables, I see in the sessions table a 
>START_TIME timestamp, which is when that session started.
>
>However, if I do QUERY SESSION F=D I get a different number, 
>"Date/Time First Data Sent:", which in some cases is blank, 
>and in other cases is a later time than the SQL start_time. 
>How is this calculated? Obviously, this is how the throughput 
>calculations are performed as it decides who is moving too 
>slowly and should be cancelled. But where does this 
>information come from (i.e. which SQL variables) and how is 
>this calculation done?

("Data/Time First Data Sent" will be blank for the control thread; it
will have an entry for the session representing the data thread.)

Remember that START_TIME in the session table marks the timetick at
which the client establishes contact with the server. The "Date/Time
First Data Sent" will come later, particularly much later if the client
is a large one. This is because the TSM client does a scan of all files
and directories prior to sending data to the TSM server.

To minimize the difference between the two events, consider the use of
the TSM Journaling Service (if the client is a windows client).
Calculating slow throughput based on calculation will give skewed
results on large TSM clients; I've seen large TSM clients that really
fast-ball the data to the server--once the directory/file scan is done,
which sometimes takes 30 minutes.

--
Mark Stapleton (stapleton AT berbee DOT com)
Mark Stapleton (stapleton AT berbee DOT com)
Berbee Information Networks
Office 262.521.5627  
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