So I have a customer that has a fairly large 5000, it started around 100 phones and a single PRI, and is now 230 IP phones with 2 PRIs and networking to another 5000 with the VM for both systems hosted locally. They are having an issue with faxes being cut-off mid-page or after one page to a fax server, occasional lag in phone operation, and extremely long reboot times (like 30 minutes to operational status)... The system only has the Processor Expansion card and not a PS-1, and the CPU utilization is typically around 75% with frequent spikes of 100% and RAM usage runs in the 60-70% range. We have recommended going to a PS-1 for this customer but they are bulking at is saying their problem is elsewhere in a misconfiguration of the 5000, but we believe it is a overloading issue and have recommended a PS-1. Their primary concern at this point is the fax cut-off issue.
My real question is, what CPU usage and RAM usage levels are acceptable and where is the level that is cause for concern?