Appendix B. The MD region manager

Table of Contents
B.1. Characteristics of Linux RAID levels
B.1.1. Linear mode
B.1.2. RAID-0
B.1.3. RAID-1
B.1.4. RAID-4/5
B.1.5. Multipath
B.2. Creating an MD region
B.2.1. RAID-0 options
B.2.2. RAID-1 options
B.2.3. RAID-4/5 options
B.3. Active and spare objects
B.3.1. Adding spare objects
B.3.2. Removing spare objects
B.3.3. Adding active objects to RAID-1
B.4. Faulty objects
B.4.1. Removing faulty objects
B.4.2. Fixing temporarily failed objects
B.4.3. Marking objects faulty
B.5. Resizing MD regions
B.5.1. Linear
B.5.2. RAID-0
B.5.3. RAID-1
B.5.4. RAID-4/5
B.6. Replacing objects

The Multi-Disk (MD) driver in the Linux kernel and the MD plug-in in EVMS provide a software implementation of RAID (Redundant Array of Inexpensive Disks). The basic idea of software RAID is to combine multiple hard disks into an array of disks in order to improve capacity, performance, and reliability.

The RAID standard defines a wide variety of methods for combining disks into a RAID array. In Linux, MD implements a subset of the full RAID standard, including RAID-0, RAID-1, RAID-4, and RAID-5. In addition, MD also supports additional combinations called Linear-RAID and Multipath.

In addition to this appendix, more information about RAID and the Linux MD driver can be found in the Software RAID HOWTO at

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