In MOSS 2007, Object Cache is enabled by default, and the memory it uses is 100MB. But because this is a site collection level setting, if there are many site collections, the overall performance might be hurt by Object Cache. This is why we always suggest our customers making tests on this setting subtly to get the best value of memory used by Object Cache.
In SharePoint 2010, there is an improvement on Object Cache setting. Although it is still a site collection level setting, now we can limit the maximum memory used by Object Cache from web app level. In Web.config of SharePoint 2010, there is a new element:
<ObjectCache maxSize="100" />. It defines the maximum memory which can be used by the object cache of this web app. If we set it to 1GB, no matter how many site collections this web app has, or how much memory the object cache of each site collection intend to use, the total size will not be bigger than 1GB.
In SharePoint 2010, Output Cache profile now can be configured on Web App level. And the profile configured on web app will overwrite the profile configured on site collection. This is a good news to web app administrator to control the use of the output cache.
<OutputCacheProfiles useCacheProfileOverrides="false" varyByHeader="" varyByParam="*" varyByCustom="" varyByRights="true" cacheForEditRights="false" />
Lots of extension names were added to BlobCache。
<BlobCache location="C:\BlobCache\14" path="\.(gif|jpg|jpeg|jpe|jfif|bmp|dib|tif|tiff|ico|png|wdp|hdp|css|js|asf|avi|flv|m4v|mov|mp3|mp4|mpeg|mpg|rm|rmvb|wma|wmv)$" maxSize="10" enabled="false" />