Managing RAID on Linux

RAID-0 (Striping)

RAID-0 is sometimes referred to simply as striping; it was not included in the original Berkeley specification and is not, strictly speaking, a form of RAID because there is no redundancy. Under RAID-0, the host system or a separate controller breaks data into blocks and writes it to different disks in round-robin fashion (as shown in Figure 2-5).

Figure 2-5. RAID-0 (striping) writes data consecutively across multiple drives.

This level yields the greatest performance and utilizes the maximum amount of available disk storage, as long as member disks are of identical sizes. Typically, if member disks are not of identical sizes, then each member of a striped array will be able to utilize only an amount of space equal to the size of the smallest member disk. Likewise, using member disks of differing speeds might introduce a bottleneck during periods of demanding I/O. See the I/O Channels and Matched drives sections, later in this chapter, for more information on the importance of using identical disks and controllers in an array.

Tip

In some implementations, stripes are organized so that all available storage space is usable. To facilitate this, data is striped across all disks until the smallest disk is full. The process repeats until no space is left on the array. The Linux kernel implements stripes in this way, but if you are working with a hardware RAID controller, ...