Selecting IO schedulers
-----------------------
To choose IO schedulers at boot time, use the argument 'elevator=deadline'.
-'noop' and 'as' (the default) are also available. IO schedulers are assigned
-globally at boot time only presently.
+'noop', 'as' and 'cfq' (the default) are also available. IO schedulers are
+assigned globally at boot time only presently. It's also possible to change
+the IO scheduler for a determined device on the fly, as described in
+Documentation/block/switching-sched.txt.
Anticipatory IO scheduler Policies
at a time during a write batch. It is this characteristic that can make
the anticipatory scheduler perform anomalously with controllers supporting
TCQ, or with hardware striped RAID devices. Setting the antic_expire
-queue paramter (see below) to zero disables this behavior, and the anticipatory
-scheduler behaves essentially like the deadline scheduler.
+queue parameter (see below) to zero disables this behavior, and the
+anticipatory scheduler behaves essentially like the deadline scheduler.
When read anticipation is enabled (antic_expire is not zero), reads
are dispatched to the disk controller one at a time.