You can choose archiving based on quota on its own, or as part of the archiving by age and quota option. The same configuration and best practice considerations apply.

You need to decide first whether you need to base archiving on quota. The default strategy of archiving based on age is more efficient, and avoids the possibility of archiving too many items.

Consider archiving based on age and quota when archiving by age only or quota only do not give the results you want. When archiving is based only on age, it may not archive enough items to keep some mailboxes within their quota. When archiving is based only on quota, some mailboxes may not come close to the Exchange mailbox storage limit. In this case, Enterprise Vault does not even archive older items.

Enterprise Vault calculates the amount of data it needs to archive to achieve the quota percentage target. It bases the calculation on estimates of the size of shortcuts. The estimates take account of any items that already have a status of pending archive. For information about how the estimates are calculated, see the following TechNote on the Enterprise Vault Support Web site:

http://entsupport.symantec.com/docs/313276

You can use the following registry values to override the values that Enterprise Vault uses in the shortcut size estimates:

See Enterprise Vault Registry Values.