You can't really RAID an IDE set. You need a SCSI subsystem which is where the "every hard disk uses its own controller" sentence comes in. The optimal for Exchange is hardware raid with the following configuration: 2 drives in RAID1 for the operating system. 2 drives in RAID1 for the Exchange logs. 3 or more drives in RAID5 for the exchange stores. The RAID1 number of drives can be reduced from two individual RAID1 sets to a pair of drives in RAID1 with two partitions. If you have to use IDE then you might do it this way: Controller 0 Primary - Operating System Controller 0 Slave - Exchange Install and Logs Controller 1 Primary - Mirrored stores Controller 1 Slave - Mirrored stores There are several options, all of which give varying degrees of resilience/performance mixes. -----Original Message----- From: Boed Yun [mailto:boedy@xxxxxxxxxxxxxx] Sent: 15 November 2002 10:32 To: [ExchangeList] Subject: [exchangelist] RAID in Exchange I am a new in IT World and have a stupid question , I've ever post this message but never get an answer. I want to build Exchange Server. and I plan to use several HD (I use all IDE both primary and secondary) , they say I could improve performance by using RAID0 or RAID5 because every harddisk use its own controller. Can I use that ? or anyone have an idea ? and sometimes I confuse about harddisk contoller. a friend told me that it's on the harddisk ( PCB attached to Harddisk) but someone else told me that it's on the motherboard or separate card. I don't know which one is correct .