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How to configure the Linux kernel/drivers/md

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Howto configure the Linux kernel / drivers / md


Block device driver configuration

Multi-device support (RAID and LVM)Edit

  • Option: MD
    • Kernel Versions: 2.6.15.6 ...
    • (on/off) Multiple devices driver support (RAID and LVM)
      Support multiple physical spindles through a single logical device. Required for RAID and logical volume management.


  • Option: BLK_DEV_MD
    • Kernel Versions: 2.6.15.6 ...
    • (on/off/module) RAID support
    • depends on MD
      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.


  • Option: MD_LINEAR
    • Kernel Versions: 2.6.15.6 ...
    • (on/off/module) Linear (append) mode
    • depends on BLK_DEV_MD
      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.


  • Option: MD_RAID0
    • Kernel Versions: 2.6.15.6 ...
    • (on/off/module) RAID-0 (striping) mode
    • depends on BLK_DEV_MD
      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.


  • Option: MD_RAID1
    • Kernel Versions: 2.6.15.6 ...
    • (on/off/module) RAID-1 (mirroring) mode
    • depends on BLK_DEV_MD
      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.


  • Option: MD_RAID10
    • Kernel Versions: 2.6.15.6 ...
    • (on/off/module) RAID-10 (mirrored striping) mode (EXPERIMENTAL)
    • depends on BLK_DEV_MD && EXPERIMENTAL
      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.


  • Option: MD_RAID5
    • Kernel Versions: 2.6.15.6 ...
    • (on/off/module) RAID-4/RAID-5 mode
    • depends on BLK_DEV_MD
      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.
      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 set, say Y. To compile this code as a module, choose M here: the module will be called raid5.
      If unsure, say Y.


  • Option: MD_RAID6
    • Kernel Versions: 2.6.15.6 ...
    • (on/off/module) RAID-6 mode
    • depends on BLK_DEV_MD
      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.
      RAID-6 requires mdadm-1.5.0 or later, available at:
      ftp://ftp.kernel.org/pub/linux/utils/raid/mdadm/
      If you want to use such a RAID-6 set, say Y. To compile this code as a module, choose M here: the module will be called raid6.
      If unsure, say Y.


  • Option: MD_MULTIPATH
    • Kernel Versions: 2.6.15.6 ...
    • (on/off/module) Multipath I/O support
    • depends on BLK_DEV_MD
      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 an IO errors arrives on the primary path.
      If unsure, say N.


  • Option: MD_FAULTY
    • Kernel Versions: 2.6.15.6 ...
    • (on/off/module) Faulty test module for MD
    • depends on BLK_DEV_MD
      The "faulty" module allows for a block device that occasionally returns read or write errors. It is useful for testing.
      In unsure, say N.


  • Option: BLK_DEV_DM
    • Kernel Versions: 2.6.15.6 ...
    • (on/off/module) Device mapper support
    • depends on MD
      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.


  • Option: DM_CRYPT
    • Kernel Versions: 2.6.15.6 ...
    • (on/off/module) Crypt target support
    • depends on BLK_DEV_DM && EXPERIMENTAL
    • select CRYPTO
      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.


  • Option: DM_SNAPSHOT
    • Kernel Versions: 2.6.15.6 ... tristate Snapshot target (EXPERIMENTAL) depends on BLK_DEV_DM && EXPERIMENTAL ---help--- Allow volume managers to take writeable snapshots of a device.


  • Option: DM_MIRROR
    • Kernel Versions: 2.6.15.6 ... 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'.


  • Option: DM_ZERO
    • Kernel Versions: 2.6.15.6 ...
    • (on/off/module) Zero target (EXPERIMENTAL)
    • depends on BLK_DEV_DM && EXPERIMENTAL
      A target that discards writes, and returns all zeroes for reads. Useful in some recovery situations.


  • Option: DM_MULTIPATH
    • Kernel Versions: 2.6.15.6 ...
    • (on/off/module) Multipath target (EXPERIMENTAL)
    • depends on BLK_DEV_DM && EXPERIMENTAL
      Allow volume managers to support multipath hardware.


  • Option: DM_MULTIPATH_EMC
    • Kernel Versions: 2.6.15.6 ...
    • (on/off/module) EMC CX/AX multipath support (EXPERIMENTAL)
    • depends on DM_MULTIPATH && BLK_DEV_DM && EXPERIMENTAL
      Multipath support for EMC CX/AX series hardware.



Linux Kernel Configuration

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