The Windows Registry was originally designed to handle small amounts of system configuration data; however over time its usage has evolved to become more of a generic system database used by all applications to store data.
With this increase in Registry usage (both in number of lookups and amount of content stored), it affects Windows performance is many ways; some subtle and some not so subtle. The most obvious impact of this is the memory consumption, however there are also other subtle problems like decreased battery life, slower IO for the rest of system, decreased system reliability and increased boot times.
New Features in Windows 8/Server 2012
• Automatic Hive Defrag: A comparison is made when loading hives at boot and during logon between the size on disk and the size in memory. An automatic defrag occurs if a significant number of bytes could be saved.
• Hot and Cold Regions: This will enable the Memory Manager to keep the most frequently accessed keys in memory and page out all the keys which are rarely accessed
• Cached File IO: Cached writes allows the disk driver and NTFS to achieve maximum throughput and minimum effort for the disk drive.
• IO Coalescing: Registry flushes occur less often and only when the IO Power Manager broadcasts it's a good time to flush modifications to disk.
• Reduced Locks: Simplified registry IO greatly reduced the number of locks needed to manage the Windows registry, leading to increased performance and reliability.