.TP
LEVEL
The manner in which the devices are arranged into the array
-(linear, raid0, raid1, raid4, raid5, raid10, multipath).
+(LINEAR, RAID0, RAID1, RAID4, RAID5, RAID10, MULTIPATH).
.TP
UUID
a 128 bit Universally Unique Identifier that identifies the array that
LEGACY ARRAYS
Early versions of the
.B md
-driver only supported Linear and Raid0 configurations and did not use
+driver only supported LINEAR and RAID0 configurations and did not use
a superblock (which is less critical with these configurations).
While such arrays should be rebuilt with superblocks if possible,
.B md
a MULTIPATH array with no superblock makes sense.
.TP
RAID1
-In some configurations it might be desired to create a raid1
+In some configurations it might be desired to create a RAID1
configuration that does not use a superblock, and to maintain the state of
the array elsewhere. While not encouraged for general use, it does
have special-purpose uses and is supported.
.SS LINEAR
-A linear array simply catenates the available space on each
+A LINEAR array simply catenates the available space on each
drive to form one large virtual drive.
One advantage of this arrangement over the more common RAID0
A MULTIPATH array is composed of a number of logically different
devices, often fibre channel interfaces, that all refer the the same
real device. If one of these interfaces fails (e.g. due to cable
-problems), the multipath driver will attempt to redirect requests to
+problems), the MULTIPATH driver will attempt to redirect requests to
another interface.
The MULTIPATH drive is not receiving any ongoing development and
multipath drivers should be preferred for new installations.
.SS FAULTY
-The FAULTY md module is provided for testing purposes. A faulty array
+The FAULTY md module is provided for testing purposes. A FAULTY array
has exactly one component device and is normally assembled without a
superblock, so the md array created provides direct access to all of
the data in the component device.
new layout. This might involve changing the number of devices in the
array (so the stripes are wider), changing the chunk size (so stripes
are deeper or shallower), or changing the arrangement of data and
-parity (possibly changing the raid level, e.g. 1 to 5 or 5 to 6).
+parity (possibly changing the RAID level, e.g. 1 to 5 or 5 to 6).
As of Linux 2.6.35, md can reshape a RAID4, RAID5, or RAID6 array to
have a different number of devices (more or fewer) and to have a
During any stripe process there is a 'critical section' during which
live data is being overwritten on disk. For the operation of
-increasing the number of drives in a raid5, this critical section
+increasing the number of drives in a RAID5, this critical section
covers the first few stripes (the number being the product of the old
and new number of devices). After this critical section is passed,
data is only written to areas of the array which no longer hold live
External metadata formats, like DDF, differ from the native MD metadata
formats in that they define a set of disks and a series of sub-arrays
within those disks. MD metadata in comparison defines a 1:1
-relationship between a set of block devices and a raid array. For
-example to create 2 arrays at different raid levels on a single
+relationship between a set of block devices and a RAID array. For
+example to create 2 arrays at different RAID levels on a single
set of disks, MD metadata requires the disks be partitioned and then
each array can be created with a subset of those partitions. The
supported external formats perform this disk carving internally.