Hello John,
Most of the time, mailbox archiving is done while mailbox users are not active. There may be occasions when mailbox archiving is needed at the same time as normal Exchange usage. This could be planned to deal with a backlog of archiving or because there is a need to archive during the day.
Enterprise Vault does not take precedence over the active mailbox users. It is not possible to extract items from an Exchange Server at the same rate when other mailbox users are active. This is generally good because archiving has less of an impact on active users. If you want to increase the archiving rate at the expense of users’ response times or decrease the archiving rate, adjust the number of concurrent connections to the Exchange Server used by the archiving process. This is a property of the archiving task.
The effect on the Exchange Server can be seen in increased CPU usage and IO per second, and in longer response times. This is discussed in the Symantec Yellow Book on Enterprise Messaging Management for Microsoft Exchange (http://www.symantec.com/enterprise/yellowbooks/index.jsp).
The principal effect on Exchange Server is on the storage system. Any effect on active users while archiving is closely related to how well specified that system is.
There are fewer I/Os on Exchange 2007 running on 64-bit, and consequently less of an impact on users of that system. Items can be extracted for archiving faster from an Exchange 2007 system.
I hope this helps !!!
