# # Block device driver configuration # if BLOCK menu "Multi-device support (RAID and LVM)" config MD bool "Multiple devices driver support (RAID and LVM)" help Support multiple physical spindles through a single logical device. Required for RAID and logical volume management. config BLK_DEV_MD tristate "RAID support" depends on MD ---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 . There you will also learn where to get the supporting user space utilities raidtools. If unsure, say N. 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 . 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 . 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 (EXPERIMENTAL)" depends on BLK_DEV_MD && EXPERIMENTAL ---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 ---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 . 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 MD_RAID5_RESHAPE bool "Support adding drives to a raid-5 array" depends on MD_RAID456 default y ---help--- A RAID-5 set can be expanded by adding extra drives. This requires "restriping" the array which means (almost) every block must be written to a different place. This option allows such restriping to be done while the array is online. You will need mdadm version 2.4.1 or later to use this feature safely. During the early stage of reshape there is a critical section where live data is being over-written. A crash during this time needs extra care for recovery. The newer mdadm takes a copy of the data in the critical section and will restore it, if necessary, after a crash. The mdadm usage is e.g. mdadm --grow /dev/md1 --raid-disks=6 to grow '/dev/md1' to having 6 disks. Note: The array can only be expanded, not contracted. There should be enough spares already present to make the new array workable. If unsure, say Y. config MD_MULTIPATH tristate "Multipath I/O support" depends on BLK_DEV_MD help Multipath-IO is the ability of certain devices to address the same physical disk over multiple 'IO paths'. The code ensures that such paths can be defined and handled at runtime, and ensures that a transparent failover to the backup path(s) happens if a IO errors arrives on the primary path. 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" depends on MD ---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 && EXPERIMENTAL ---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 && EXPERIMENTAL select CRYPTO ---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 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 (EXPERIMENTAL)" depends on BLK_DEV_DM && EXPERIMENTAL ---help--- Allow volume managers to take writable snapshots of a device. config DM_MIRROR tristate "Mirror target (EXPERIMENTAL)" depends on BLK_DEV_DM && EXPERIMENTAL ---help--- Allow volume managers to mirror logical volumes, also needed for live data migration tools such as 'pvmove'. config DM_ZERO tristate "Zero target (EXPERIMENTAL)" depends on BLK_DEV_DM && EXPERIMENTAL ---help--- A target that discards writes, and returns all zeroes for reads. Useful in some recovery situations. config DM_MULTIPATH tristate "Multipath target (EXPERIMENTAL)" depends on BLK_DEV_DM && EXPERIMENTAL ---help--- Allow volume managers to support multipath hardware. config DM_MULTIPATH_EMC tristate "EMC CX/AX multipath support (EXPERIMENTAL)" depends on DM_MULTIPATH && BLK_DEV_DM && EXPERIMENTAL ---help--- Multipath support for EMC CX/AX series hardware. endmenu endif