I mentioned Kerio Archiver for user mailboxes the other day and had several customers ask me what effect archiving messages might have on performance. That's a hard question to answer, because performance can be affected by so many things, but there is a way to get an idea.
First of all, realize that this issue affects all mailservers. For example, here is a Technet article recommending limiting key folders to no more than 5,000 messages with Exchange. I'll just quote one paragraph from that page:
What are key folders? For Kerio, those would be INBOX and Sent Items. For users who refuse to clean Deleted Items, we can add that. The INBOX is of course the most heavily used - every time new email arrives that folder must be updated and every time a user accesses their email it has to be searched and sorted.
You can get an idea of how much of that goes on by turning on Message Store -> Searching and Sorting in your debug log. First, right click in the log itself and select "Messages".
Then choose "Searching and Sorting" under Message Store.
You'll see messages like this as people log in and out:
That's from my session with only a few hundred messages in my INBOX. Don't forget to turn that debug message off when you have what you need.
Looking at that for your large mailboxes should give you an idea of the workload caused by these. However, I do need to mention that archiving is not the whole solution when mailboxes have been allowed to grow unchecked. The problem is that when large folders are created, deleting messages leaves just as many empty slots which do have to be searched - you'll save on sorting time, but searching will take almost as long.
There is a way to fix that: stop the Kerio server and (using your operating system tools) rename the INBOX to another name. Restart the server and when the user accesses mail, an empty INBOX will be created for them. If you regularly use a tool like the Archiver after that, the mailbox will not have that "empty slot" issue.
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More Articles by Anthony Lawrence © 2014-12-17 Anthony Lawrence
I was taught that the human brain was the crowning glory of evolution so far, but I think it’s a very poor scheme for survival (Kurt Vonnegut).