Software Installation and User’s Guide141ICP RAID Console10.5.4.3 Notes on the Configuration of RAID 0, 1, 4, 5 and 10 Arrays DrivesUse logical drives of the typedisk to build an array drive.RAID array drives can be configured with logical drives of the type chain also, butsecurity should be taken into consideration. For regular RAID array drives, type disklogical drives are used.Logical drives of an array drive should have the same storage capacity.To avoid wasting valuable storage capacity, use only logical drives that have the samestorage capacity as the logical drive being replaced on that array.A hot fix drive provides the most security.One of the reasons RAID array drives are used, lies with the data redundancy theyprovide, that is, the data security you have in the event of a hard disk failure. For thepurpose of the following considerations, we define the term time without redundancy(TWR) as the time it takes to replace a failed hard drive (assuming there is no hot fix driveinstalled in the system). The time without redundancy should be kept as short as possible,not including the time needed to set up the array drive (state build).Assume that one of the hard disks of a RAID 5 array drive has failed. The array drive iswithout redundancy. TWR begins. Any superfluous prolongation of the TWR (becauseyou have to get a replacement hard disk, or because no one checked the file server)increases the risk of data loss should a second hard disk fail. Therefore, new redundancyshould be created as soon as possible and in an entirely automated manner. Integrate a hotfix drive as an immediately available and auto-replacing hard disk to keep the TWR asshort as possible. Only a hot fix drive can ensure optimal array drive security and constantdata availability. Of course a hot fix drive is not mandatory. If you control the array driveat regular intervals and immediately replace a defective hard disk (by shutting down thesystem or using a hot fix), you can minimize the risk of data loss.10.5.5 Configure Host DrivesThe Configure Host Drives option (Figure 10-104) allows you to configure host drives(level of hierarchy 4). These are the drives the host computer is aware of. Host drives canconsist of a single hard disk, or of many hard disks built to create a RAID 5 array drive.This menu option is similar to the Configure Host Drives option in Express Setup (seeSection 10.4.1). Unlike Express Setup, Advanced Setup allows the user to select a stripesize while Express Setup defaults the stripe size to 128KB. Also, Advanced Setup has theSplit Host Drive, Merge Host Drives, and Partition Drive menu options.The additional capacity resulting from an online capacity expansion is shown as anotherhost drive. If you expand the capacity of the array drive a second time, there would bethree host drives belonging to the same array drive. Since there is currently no operatingsystem which supports “growing hard disks”, this expansion method is the only safe wayto introduce new capacity.
