## 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_BUFIO       tristate       depends on BLK_DEV_DM && EXPERIMENTAL       ---help---	 This interface allows you to do buffered I/O on a device and acts	 as a cache, holding recently-read blocks in memory and performing	 delayed writes. source "drivers/md/persistent-data/Kconfig" 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_THIN_PROVISIONING       tristate "Thin provisioning target (EXPERIMENTAL)"       depends on BLK_DEV_DM && EXPERIMENTAL       select DM_PERSISTENT_DATA       ---help---         Provides thin provisioning and snapshots that share a data store. config DM_DEBUG_BLOCK_STACK_TRACING	boolean "Keep stack trace of thin provisioning block lock holders"	depends on STACKTRACE_SUPPORT && DM_THIN_PROVISIONING	select STACKTRACE	---help---	  Enable this for messages that may help debug problems with the	  block manager locking used by thin provisioning. 	  If unsure, say N. config DM_DEBUG_SPACE_MAPS	boolean "Extra validation for thin provisioning space maps"	depends on DM_THIN_PROVISIONING	---help---	  Enable this for messages that may help debug problems with the	  space maps used by thin provisioning.           If unsure, say N. 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"       depends on BLK_DEV_DM       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"	depends on BLK_DEV_DM	---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. config DM_VERITY	tristate "Verity target support (EXPERIMENTAL)"	depends on BLK_DEV_DM && EXPERIMENTAL	select CRYPTO	select CRYPTO_HASH	select DM_BUFIO	---help---	  This device-mapper target creates a read-only device that	  transparently validates the data on one underlying device against	  a pre-generated tree of cryptographic checksums stored on a second	  device. 	  You'll need to activate the digests you're going to use in the	  cryptoapi configuration. 	  To compile this code as a module, choose M here: the module will	  be called dm-verity. 	  If unsure, say N. endif # MD