Dell PERC 4/DC - Manual (Page 22)

Hot Spares
Any hard drive that is present, formatted, and initialized, but is not included in an array or logical drive, can be designated as a hot spare. A hot spare should
have the same or greater capacity than the smallest physical disk in the array it protects. You can designate hard drives as hot spares using your array
management software.
Logical Drives
Logical drives, also known as virtual disks, are arrays or spanned arrays that are available to the operating system. The storage space in a logical drive is
spread across all the physical drives in the array or spanned arrays.
You must create one or more logical drives for each array, and the logical drive capacity must include all of the drive space in an array. You can make the logical
drive capacity larger by spanning arrays. In an array of drives with mixed sizes, the smallest common drive size is used and the space in larger drives is not
used. The RAID controller supports up to 40 logical drives.
Configuration Strategies
The most important factors in RAID array configuration are:
l Drive capacity
l Drive availability (fault tolerance)
l Drive performance
You cannot configure a logical drive that optimizes all three factors, but it is easy to choose a logical drive configuration that maximizes one factor at the
expense of the other two factors. For example, RAID 1(mirroring) provides excellent fault tolerance, but requires a redundant drive.
Configuring Logical Drives
After you have attached all physical drives, perform the following steps to prepare a logical drive. If the operating system is not yet installed, use the BIOS
Configuration Utility to perform this procedure. If the operating system is installed, you can use the Dell Manager for Linux or OpenManage Array Manager (for
Windows and Netware), depending on the operating system.
1. Start the system.
2. Run your array management software.
3. Select the option to customize the RAID array.
In the BIOS Configuration Utility and Dell Manager for Linux, use either Easy Configuration or New Configuration to customize the RAID array.
4. Create and configure one or more system drives (logical drives).
5. Select the RAID level, cache policy, read policy, and write policy.
6. Save the configuration.
7. Initialize the system drives.
After initialization, you can install the operating system.
See BIOS Configuration Utility and Dell Manager for detailed configuration instructions.
CAUTION: If you select New Configuration, all previous configuration information will be deleted.
NOTE: Refer to the section Summary of RAID Levels for RAID level explanations.