In SharePoint 2010 we removed StorMan.aspx (Storage Space Allocation) (see http://support.microsoft.com/kb/982587/EN-US) which in previous versions of SharePoint enabled granular management and insight into storage. For example, the page would show you the top 100 documents or document libraries in terms of size. With that information end users could the page to clean up content from their site(s) by deleting the large content that they no longer needed. In Service Pack 1 we are bringing back an improved StorMan.aspx, enabling users to better understand where their quota is going and act upon that information to reduce the size of their sites.
Storage Metrics provide insight into how storage is being used across Site Collections and Sites enabling administrators and owners to quickly identify content that can be archived or removed in order to remain within their allocated quotas.
To begin using Storage Metrics select Site Actions, and then click Site Settings.
From Site Settings select Storage Metrics under Site Collection Administration (see Figure 1 Site Settings http://sharepoint.contoso.com/).
Figure 1 Site Settings http://sharepoint.contoso.com/
Storage metrics will be displayed for the selected Site Collection/Site (see Figure 2 Storage Metrics http://sharepoint.contoso.com/).
Figure 2 Storage Metrics http://sharepoint.contoso.com/
To learn more about Service Pack 1 for SharePoint 2010 see my post on the SharePoint Team Blog at http://sharepoint.microsoft.com/blog/Pages/BlogPost.aspx?pID=973.