-''' Copyright Neil Brown and others.
-''' This program is free software; you can redistribute it and/or modify
-''' it under the terms of the GNU General Public License as published by
-''' the Free Software Foundation; either version 2 of the License, or
-''' (at your option) any later version.
-''' See file COPYING in distribution for details.
+.\" Copyright Neil Brown and others.
+.\" This program is free software; you can redistribute it and/or modify
+.\" it under the terms of the GNU General Public License as published by
+.\" the Free Software Foundation; either version 2 of the License, or
+.\" (at your option) any later version.
+.\" See file COPYING in distribution for details.
.TH MD 4
.SH NAME
md \- Multiple Device driver aka Linux Software RAID
.B md
driver provides virtual devices that are created from one or more
independent underlying devices. This array of devices often contains
-redundancy, and hence the acronym RAID which stands for a Redundant
-Array of Independent Devices.
+redundancy and the devices are often disk drives, hence the acronym RAID
+which stands for a Redundant Array of Independent Disks.
.PP
.B md
supports RAID levels
not, then only the amount of space available on the smallest device is
used (any extra space on other devices is wasted).
+Note that the read balancing done by the driver does not make the RAID1
+performance profile be the same as for RAID0; a single stream of
+sequential input will not be accelerated (e.g. a single dd), but
+multiple sequential streams or a random workload will use more than one
+spindle. In theory, having an N-disk RAID1 will allow N sequential
+threads to read from all disks.
+
.SS RAID4
A RAID4 array is like a RAID0 array with an extra device for storing
projects / thirdparty / mdadm.git / blobdiff