Chapter 6: Modifying Your Direct Attached Storage ● 59Understanding Logical DrivesA logical drive is a group of physical disk drives that appears to your operating system as asingle drive that can be used for storing data.A logical drive can comprise one or more disk drives and can use part or all of each disk drive’scapacity.It is possible to include the same disk drive in two different logical drives by using just aportion of the space on the disk drive in each, as shown in the following figure.Disk drive space that has been assigned to a logical drive is called a segment. A segment caninclude all or just a portion of a disk drive’s space. A disk drive with one segment is part of onelogical drive, a disk drive with two segments is part of two logical drives, and so on. A segmentcan be part of only one logical drive. When a logical drive is deleted, the segments thatcomprised it revert to available space (or free segments).A logical drive can include redundancy, depending on the RAID level assigned to it. (SeeSelecting the Best RAID Level on page 152 for more information.)Once a logical drive has been created, you can change its RAID level or increase its capacity tomeet changing requirements. You can also protect your logical drives by assigning one or morehot spares to them. (See page 54 for more information.)Three Disk Drives(500 MB Each)One RAID 5 LogicalDriveOne RAID 1Logical Drive250 MB250 MB250 MB250 MB250 MB250 MB 250 MB250 MB250 MB250 MBAvailableSpaceAppears to OperatingSystem as one250 MB disk driveAppears to OperatingSystem as one500 MB disk drive
