HiMicrosoft Recormend add 1 Mailbox database per 1 Stroage Group.WHat is advantage of that ?REgards

Transaction logs are shared/common for all databases of a Storage Group so it is good to have only one database in storage group for database management, maintenance andrecoverypurpose. Moreover you can enable continuous replication (CCR, LCR, SCR) only in case SG has one DB inside.Amit Tank | MVP Exchange Server | MCITP: EMA, MCSA: M | http://ExchangeShare.WordPress.com

GayanWIC,As Amit has already posted, having one store per storage groups has its own benifits. When you create a storage group with multiple stores the backup software has to look at the more number of log files created for multiple stores under it and while backing up the stores number of IOPs is high. That may cause a problem when a backup is runinng. For recovery purposes having a store under each storage groups provides you granularity to choose from available backups very quick. For Exchange 2007 high availability options it is highly recommended you use a single store per storage group rather HA in E2K7 can not be configured unless. So, the whole thing revolves around the disk performance and so around the database performance as well. It is highly useful when you have backups scheduled which may conflictwith peak hours.MMilind Naphade | MCTS:M | http://www.msexchangegeek.com

Try this link http://technet.microsoft.com/en-us/library/bb331954.aspxAndrew Sword, MVP