v0.54, 21 November 1998
RAID stands for ''Redundant Array of Inexpensive Disks'', and
is meant to be a way of creating a fast and reliable disk-drive
subsystem out of individual disks. RAID can guard against disk failure, and can also improve performance over that of a single disk drive.
This document is a tutorial/HOWTO/FAQ for users of
the Linux MD kernel extension, the associated tools, and their use.
The MD extension implements RAID-0 (striping), RAID-1 (mirroring),
RAID-4 and RAID-5 in software. That is, with MD, no special hardware
or disk controllers are required to get many of the benefits of RAID.
This document is copyrighted and GPL'ed by Linas Vepstas
Permission to use, copy, distribute this document for any purpose is
hereby granted, provided that the author's / editor's name and
this notice appear in all copies and/or supporting documents; and
that an unmodified version of this document is made freely available.
This document is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY, either expressed or implied. While every effort
has been taken to ensure the accuracy of the information documented
herein, the author / editor / maintainer assumes NO RESPONSIBILITY
for any errors, or for any damages, direct or consequential, as a
result of the use of the information documented herein.
RAID, although designed to improve system reliability by adding
redundancy, can also lead to a false sense of security and confidence
when used improperly. This false confidence can lead to even greater
disasters. In particular, note that RAID is designed to protect against
*disk* failures, and not against *power* failures or *operator*
mistakes. Power failures, buggy development kernels, or operator/admin
errors can lead to damaged data that it is not recoverable!
RAID is *not* a substitute for proper backup of your system.
Know what you are doing, test, be knowledgeable and aware!