Guide to configuring the linux kernel/Block layer/IO Schedulers

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 * Guide to configuring the linux kernel

=Main= LBD bool "Support for Large Block Devices" depends on X86 || (MIPS && 32BIT) || PPC32 || ARCH_S390_31 || SUPERH || UML help Say Y here if you want to attach large (bigger than 2TB) discs to	 your machine, or if you want to have a raid or loopback device bigger than 2TB. Otherwise say N.

I/O Schedulers
menu "IO Schedulers"

config IOSCHED_NOOP bool default y	---help--- The no-op I/O scheduler is a minimal scheduler that does basic merging and sorting. Its main uses include non-disk based block devices like memory devices, and specialised software or hardware environments that do their own scheduling and require only minimal assistance from the kernel.

config IOSCHED_AS tristate "Anticipatory I/O scheduler" default y	---help--- The anticipatory I/O scheduler is the default disk scheduler. It is	 generally a good choice for most environments, but is quite large and complex when compared to the deadline I/O scheduler, it can also be slower in some cases especially some database loads.

config IOSCHED_DEADLINE tristate "Deadline I/O scheduler" default y	---help--- The deadline I/O scheduler is simple and compact, and is often as	 good as the anticipatory I/O scheduler, and in some database workloads, better. In the case of a single process performing I/O to	 a disk at any one time, its behaviour is almost identical to the anticipatory I/O scheduler and so is a good choice.

config IOSCHED_CFQ tristate "CFQ I/O scheduler" default y	---help--- The CFQ I/O scheduler tries to distribute bandwidth equally among all processes in the system. It should provide a fair working environment, suitable for desktop systems.

choice prompt "Default I/O scheduler" default DEFAULT_AS help Select the I/O scheduler which will be used by default for all block devices.

config DEFAULT_AS bool "Anticipatory" if IOSCHED_AS=y

config DEFAULT_DEADLINE bool "Deadline" if IOSCHED_DEADLINE=y

config DEFAULT_CFQ bool "CFQ" if IOSCHED_CFQ=y

config DEFAULT_NOOP bool "No-op"

endchoice

config DEFAULT_IOSCHED string default "anticipatory" if DEFAULT_AS default "deadline" if DEFAULT_DEADLINE default "cfq" if DEFAULT_CFQ default "noop" if DEFAULT_NOOP

endmenu