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linux/drivers/md/Kconfig
Jonathan Brassow b12d437b73 dm raid: support metadata devices 
Add the ability to parse and use metadata devices to dm-raid.  Although
not strictly required, without the metadata devices, many features of
RAID are unavailable.  They are used to store a superblock and bitmap.

The role, or position in the array, of each device must be recorded in
its superblock.  This is to help with fault handling, array reshaping,
and sanity checks.  RAID 4/5/6 devices must be loaded in a specific order:
in this way, the 'array_position' field helps validate the correctness
of the mapping when it is loaded.  It can be used during reshaping to
identify which devices are added/removed.  Fault handling is impossible
without this field.  For example, when a device fails it is recorded in
the superblock.  If this is a RAID1 device and the offending device is
removed from the array, there must be a way during subsequent array
assembly to determine that the failed device was the one removed.  This
is done by correlating the 'array_position' field and the bit-field
variable 'failed_devices'.

Signed-off-by: Jonathan Brassow <jbrassow@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2011-08-02 12:32:07 +01:00

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#
# Block device driver configuration
#
menuconfig MD
bool "Multiple devices driver support (RAID and LVM)"
depends on BLOCK
help
Support multiple physical spindles through a single logical device.
Required for RAID and logical volume management.
if MD
config BLK_DEV_MD
tristate "RAID support"
---help---
This driver lets you combine several hard disk partitions into one
logical block device. This can be used to simply append one
partition to another one or to combine several redundant hard disks
into a RAID1/4/5 device so as to provide protection against hard
disk failures. This is called "Software RAID" since the combining of
the partitions is done by the kernel. "Hardware RAID" means that the
combining is done by a dedicated controller; if you have such a
controller, you do not need to say Y here.
More information about Software RAID on Linux is contained in the
Software RAID mini-HOWTO, available from
<http://www.tldp.org/docs.html#howto>. There you will also learn
where to get the supporting user space utilities raidtools.
If unsure, say N.
config MD_AUTODETECT
bool "Autodetect RAID arrays during kernel boot"
depends on BLK_DEV_MD=y
default y
---help---
If you say Y here, then the kernel will try to autodetect raid
arrays as part of its boot process.
If you don't use raid and say Y, this autodetection can cause
a several-second delay in the boot time due to various
synchronisation steps that are part of this step.
If unsure, say Y.
config MD_LINEAR
tristate "Linear (append) mode"
depends on BLK_DEV_MD
---help---
If you say Y here, then your multiple devices driver will be able to
use the so-called linear mode, i.e. it will combine the hard disk
partitions by simply appending one to the other.
To compile this as a module, choose M here: the module
will be called linear.
If unsure, say Y.
config MD_RAID0
tristate "RAID-0 (striping) mode"
depends on BLK_DEV_MD
---help---
If you say Y here, then your multiple devices driver will be able to
use the so-called raid0 mode, i.e. it will combine the hard disk
partitions into one logical device in such a fashion as to fill them
up evenly, one chunk here and one chunk there. This will increase
the throughput rate if the partitions reside on distinct disks.
Information about Software RAID on Linux is contained in the
Software-RAID mini-HOWTO, available from
<http://www.tldp.org/docs.html#howto>. There you will also
learn where to get the supporting user space utilities raidtools.
To compile this as a module, choose M here: the module
will be called raid0.
If unsure, say Y.
config MD_RAID1
tristate "RAID-1 (mirroring) mode"
depends on BLK_DEV_MD
---help---
A RAID-1 set consists of several disk drives which are exact copies
of each other. In the event of a mirror failure, the RAID driver
will continue to use the operational mirrors in the set, providing
an error free MD (multiple device) to the higher levels of the
kernel. In a set with N drives, the available space is the capacity
of a single drive, and the set protects against a failure of (N - 1)
drives.
Information about Software RAID on Linux is contained in the
Software-RAID mini-HOWTO, available from
<http://www.tldp.org/docs.html#howto>. There you will also
learn where to get the supporting user space utilities raidtools.
If you want to use such a RAID-1 set, say Y. To compile this code
as a module, choose M here: the module will be called raid1.
If unsure, say Y.
config MD_RAID10
tristate "RAID-10 (mirrored striping) mode"
depends on BLK_DEV_MD
---help---
RAID-10 provides a combination of striping (RAID-0) and
mirroring (RAID-1) with easier configuration and more flexible
layout.
Unlike RAID-0, but like RAID-1, RAID-10 requires all devices to
be the same size (or at least, only as much as the smallest device
will be used).
RAID-10 provides a variety of layouts that provide different levels
of redundancy and performance.
RAID-10 requires mdadm-1.7.0 or later, available at:
ftp://ftp.kernel.org/pub/linux/utils/raid/mdadm/
If unsure, say Y.
config MD_RAID456
tristate "RAID-4/RAID-5/RAID-6 mode"
depends on BLK_DEV_MD
select RAID6_PQ
select ASYNC_MEMCPY
select ASYNC_XOR
select ASYNC_PQ
select ASYNC_RAID6_RECOV
---help---
A RAID-5 set of N drives with a capacity of C MB per drive provides
the capacity of C * (N - 1) MB, and protects against a failure
of a single drive. For a given sector (row) number, (N - 1) drives
contain data sectors, and one drive contains the parity protection.
For a RAID-4 set, the parity blocks are present on a single drive,
while a RAID-5 set distributes the parity across the drives in one
of the available parity distribution methods.
A RAID-6 set of N drives with a capacity of C MB per drive
provides the capacity of C * (N - 2) MB, and protects
against a failure of any two drives. For a given sector
(row) number, (N - 2) drives contain data sectors, and two
drives contains two independent redundancy syndromes. Like
RAID-5, RAID-6 distributes the syndromes across the drives
in one of the available parity distribution methods.
Information about Software RAID on Linux is contained in the
Software-RAID mini-HOWTO, available from
<http://www.tldp.org/docs.html#howto>. There you will also
learn where to get the supporting user space utilities raidtools.
If you want to use such a RAID-4/RAID-5/RAID-6 set, say Y. To
compile this code as a module, choose M here: the module
will be called raid456.
If unsure, say Y.
config MULTICORE_RAID456
bool "RAID-4/RAID-5/RAID-6 Multicore processing (EXPERIMENTAL)"
depends on MD_RAID456
depends on SMP
depends on EXPERIMENTAL
---help---
Enable the raid456 module to dispatch per-stripe raid operations to a
thread pool.
If unsure, say N.
config MD_MULTIPATH
tristate "Multipath I/O support"
depends on BLK_DEV_MD
help
MD_MULTIPATH provides a simple multi-path personality for use
the MD framework. It is not under active development. New
projects should consider using DM_MULTIPATH which has more
features and more testing.
If unsure, say N.
config MD_FAULTY
tristate "Faulty test module for MD"
depends on BLK_DEV_MD
help
The "faulty" module allows for a block device that occasionally returns
read or write errors. It is useful for testing.
In unsure, say N.
config BLK_DEV_DM
tristate "Device mapper support"
---help---
Device-mapper is a low level volume manager. It works by allowing
people to specify mappings for ranges of logical sectors. Various
mapping types are available, in addition people may write their own
modules containing custom mappings if they wish.
Higher level volume managers such as LVM2 use this driver.
To compile this as a module, choose M here: the module will be
called dm-mod.
If unsure, say N.
config DM_DEBUG
boolean "Device mapper debugging support"
depends on BLK_DEV_DM
---help---
Enable this for messages that may help debug device-mapper problems.
If unsure, say N.
config DM_CRYPT
tristate "Crypt target support"
depends on BLK_DEV_DM
select CRYPTO
select CRYPTO_CBC
---help---
This device-mapper target allows you to create a device that
transparently encrypts the data on it. You'll need to activate
the ciphers you're going to use in the cryptoapi configuration.
Information on how to use dm-crypt can be found on
<http://www.saout.de/misc/dm-crypt/>
To compile this code as a module, choose M here: the module will
be called dm-crypt.
If unsure, say N.
config DM_SNAPSHOT
tristate "Snapshot target"
depends on BLK_DEV_DM
---help---
Allow volume managers to take writable snapshots of a device.
config DM_MIRROR
tristate "Mirror target"
depends on BLK_DEV_DM
---help---
Allow volume managers to mirror logical volumes, also
needed for live data migration tools such as 'pvmove'.
config DM_RAID
tristate "RAID 1/4/5/6 target (EXPERIMENTAL)"
depends on BLK_DEV_DM && EXPERIMENTAL
select MD_RAID1
select MD_RAID456
select BLK_DEV_MD
---help---
A dm target that supports RAID1, RAID4, RAID5 and RAID6 mappings
A RAID-5 set of N drives with a capacity of C MB per drive provides
the capacity of C * (N - 1) MB, and protects against a failure
of a single drive. For a given sector (row) number, (N - 1) drives
contain data sectors, and one drive contains the parity protection.
For a RAID-4 set, the parity blocks are present on a single drive,
while a RAID-5 set distributes the parity across the drives in one
of the available parity distribution methods.
A RAID-6 set of N drives with a capacity of C MB per drive
provides the capacity of C * (N - 2) MB, and protects
against a failure of any two drives. For a given sector
(row) number, (N - 2) drives contain data sectors, and two
drives contains two independent redundancy syndromes. Like
RAID-5, RAID-6 distributes the syndromes across the drives
in one of the available parity distribution methods.
config DM_LOG_USERSPACE
tristate "Mirror userspace logging (EXPERIMENTAL)"
depends on DM_MIRROR && EXPERIMENTAL && NET
select CONNECTOR
---help---
The userspace logging module provides a mechanism for
relaying the dm-dirty-log API to userspace. Log designs
which are more suited to userspace implementation (e.g.
shared storage logs) or experimental logs can be implemented
by leveraging this framework.
config DM_ZERO
tristate "Zero target"
depends on BLK_DEV_DM
---help---
A target that discards writes, and returns all zeroes for
reads. Useful in some recovery situations.
config DM_MULTIPATH
tristate "Multipath target"
depends on BLK_DEV_DM
# nasty syntax but means make DM_MULTIPATH independent
# of SCSI_DH if the latter isn't defined but if
# it is, DM_MULTIPATH must depend on it. We get a build
# error if SCSI_DH=m and DM_MULTIPATH=y
depends on SCSI_DH || !SCSI_DH
---help---
Allow volume managers to support multipath hardware.
config DM_MULTIPATH_QL
tristate "I/O Path Selector based on the number of in-flight I/Os"
depends on DM_MULTIPATH
---help---
This path selector is a dynamic load balancer which selects
the path with the least number of in-flight I/Os.
If unsure, say N.
config DM_MULTIPATH_ST
tristate "I/O Path Selector based on the service time"
depends on DM_MULTIPATH
---help---
This path selector is a dynamic load balancer which selects
the path expected to complete the incoming I/O in the shortest
time.
If unsure, say N.
config DM_DELAY
tristate "I/O delaying target (EXPERIMENTAL)"
depends on BLK_DEV_DM && EXPERIMENTAL
---help---
A target that delays reads and/or writes and can send
them to different devices. Useful for testing.
If unsure, say N.
config DM_UEVENT
bool "DM uevents (EXPERIMENTAL)"
depends on BLK_DEV_DM && EXPERIMENTAL
---help---
Generate udev events for DM events.
config DM_FLAKEY
tristate "Flakey target (EXPERIMENTAL)"
depends on BLK_DEV_DM && EXPERIMENTAL
---help---
A target that intermittently fails I/O for debugging purposes.
endif # MD
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