How can I improve the performance of the GMS Collaboration Server?

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Question

GMS Collaboration uses the IMAP protocol to retrieve email messages from the server. It is possible to significantly alter the fetch response time of these messages but this will depend on factors outside the control of GMS.

These factors include the Operating System, the TCP/IP stack and the performance of the Local Area Network.

The IMAP service will buffer 32Kb of data by as its default value. It will proceed to send this out to the retrieving e-mail client in single bursts per 32Kb blocks. This can be extremely efficient on one network and less efficient on another. To suit the multiple environments of our customers, we have allowed for the buffer to be changeable.

Answer

You will need to perform at least two tests in order to determine whether IMAP is already working as it efficiently as it can, or whether it can be tweaked to perform better.

Send yourself a test message with an attachment approximately 5MB’s in size. Once this message is received by your e-mail client, copy/move it to another IMAP folder. Now select that folder and then select the message. Take note as to how long this operation takes to complete.

You will now need to change the IMAP buffer variable ready for the second test.

Navigate to the system variables page of the administration interface. If this is disabled, please see the article at the bottom of this page.

Scroll down the list of variables and look for a variable named "IMAPFetchBufferSize". Highlight it and click on Edit. The default value for this variable should be 32 as used in your test. Now try changing this to 8, then click on Update, and monitor whether this improves performance.

If the variable does not exist on your system it will be using the default value of 32. Nevertheless, create the variable and follow the same instructions above.

With IMAPFetchBufferSize now set to 8, copy/move the message back into a new folder. Now select this folder and select the message. When this completes does it seem faster or slower than previously?

If the results seem negligible, you may choose to return this value to 32. Alternatively if you have a support contract, Gordano support will be happy to interrogate your IMAP log to determine exactly how long it took for the server to send both messages to the client.

Gordano testing

The results that we concluded varied dramatically based on the Operating System of the server. We discovered that 32KB is very fast on Solaris, but not so fast on Windows NT 4.0 which works faster sending 8KB blocks of data. To highlight the improvement we saw on our Windows network, a 9MB message took 1 minute to display on an NT4 server with the buffer set at 32KB. The same message took 5 seconds to display with the buffer set at 8KB.

No restart of the IMAP service is required after this change but you must restart your email client.
If you are in any doubt that the recent modification has NOT increased performance, set the value back to the default (32).

See Also:

Keywords:imap collab collaboration performance speed fetch IMAPFetchBufferSize

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