#Softraid linux driver
#Softraid linux manual
#Softraid linux software

It does not try to find out if a path that has previously failed might be working again.

#Softraid linux driver

The kernel portion of the md multipath driver only handles routing I/O requests to the proper device and handling failures on the active path.

#Softraid linux software

The linux kernel implements multipath disk access via the software RAID stack known as the md (Multiple Devices) driver. The program was used to monitor multipath ( RAID) devices, and is usually started at boot time as a service, and afterwards running as a daemon.Д®nterprise storage requirements often include the desire to have more than one way to talk to a single disk drive so that in the event of some failure to talk to a disk drive via one controller, the system can automatically switch to another controller and keep going. Mdmpd was a daemon used for monitoring MD multipath devices up to Linux kernel 2.6.10-rc1, developed by Red Hat as part of the mdadm package.

Volume metadata format used by the Intel Rapid Storage Technology(RST), former Intel Matrix RAID, implemented on many consumer-level motherboards.

DDF ( Disk Data Format), an industry standard defined by the Storage Networking Industry Association for increased interoperability.

ДЄs of OctoberВ 2013, there are two supported formats of the external metadata: This allows Linux to use various firmware- or driver-based RAID volumes, also known as ' fake RAID'.

#Softraid linux manual

This approach allows the /boot filesystem to be inside any RAID system without the need of a complex manual configuration.Д«esides its own formats for RAID volumes metadata, Linux software RAID also supports external metadata formats, since version 2.6.27 of the Linux kernel and version 3.0 of the mdadm userspace utility. With more recent bootloaders it is possible to load the MD support as a kernel module through the initramfs mechanism. This will result in a catch-up, but /boot filesystems are usually small. In the latter case the system will boot by treating the RAID1 device as a normal filesystem, and once the system is running it can be remounted as md and the second disk added to it. In order to circumvent this problem a /boot filesystem must be used either without md support, or else with RAID1. Although normally present, it may not be present for GRUB 2. Specifically it will not be present if the boot loader is either (e)LiLo or GRUB legacy. Since support for MD is found in the kernel, there is an issue with using it before the kernel is running. Since version 3.7 of the Linux kernel mainline, md supports TRIM operations for the underlying solid-state drives (SSDs), for linear, RAIDВ 0, RAIDВ 1, RAIDВ 5 and RAIDВ 10 layouts. Since version 2.6.28 of the Linux kernel mainline, non-partitionable arrays can be partitioned, the partitions being referred to in the same way as for partitionable arraysВ вЂ“ for example, /dev/md/md1p2.

The partitions were identified by adding p, where is the partition number thus /dev/md/md_d2p3 for example. The device names were modified by changing md to md_d. Since 2.6.x kernels, a new type of MD device was introduced, a partitionable array. Under 2.4.x kernels and earlier these two were the only options. More recent kernels have support for names such as /dev/md/Home. The original (standard) form of names for md devices is /dev/md, where is a number between 0 and 99. Container вЂ“ a group of devices managed as a single device, in which one can build RAID systems.

Faulty вЂ“ a single device which emulates a number of disk-fault scenarios for testing and development.

Multipath вЂ“ provides multiple paths with failover to a single device.

Linear вЂ“ concatenates a number of devices into a single large MD device.

Which of the two setups is preferable depends on the details of the application in question, such as whether or not spare disks are available, and how they should be spun up. A single-drive failure in a RAIDВ 0+1 configuration results in one of the lower-level stripes completely failing, and the top-level mirror entering degraded mode. A single-drive failure in a RAIDВ 10 configuration results in one of the lower-level mirrors entering degraded mode, but the top-level stripe performing normally (except for the performance hit). RAIDВ 10 is distinct from RAID 0+1, which consists of a top-level RAIDВ 1 mirror composed of high-performance RAIDВ 0 stripes directly across the physical hard disks.

RAIDВ 10 вЂ“ Take a number of RAIDВ 1 mirrorsets and stripe across them RAIDВ 0 style.

RAIDВ 6 вЂ“ Like RAIDВ 5, but with two parity segments per stripe.

RAIDВ 5 вЂ“ Like RAIDВ 4, but with the parity distributed across all devices.

RAIDВ 4 вЂ“ Like RAIDВ 0, but with an extra device for the parity.

MD can handle devices of different lengths, the extra space on the larger device is then not striped.