efficiency drops when user exceed 5000+?

[Zhang Weiwu]

Hello. I have cyrus imapd runing now on my server. Today I heard people 
say when the user number exceed 5000+ the cyrus proformance drops in the 
way that unless many partitions ware made (what partition? file system 
partition?) to share the load. I'm pretty newbie on mail server 
administration, should I start to do something in case my user number 
grow over 5000+? I'm running a dual-processor Xeon server with IDE soft 
RAID10 discs.
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