What is Pool Slicing?
Pool Slicing is a new feature that comes with SQL Server 2008 R2 that allows Garbage Collection of pools to happen incrementally, i.e. one slice at a time instead of the whole pool at one go. The slicing is done based on the create timestamp of the blob. This allows making incremental progress on garbage collecting huge pools that contain hundreds of millions of blobs without requiring a long maintenance window.
Still confused? What pools? Ok, let's solve the mistery - it's about Remote Blob Storage Pools. No, don't look the information in Books Online yet. You can find details on the SQL Remote Blob Storage Team Blog
in this article: Running RBS Maintainer
Source: Microsoft SQL Server - Facebook page