# This file contains the rules to customize io scheduler.

# Heuristics:
# 'deadline' io-scheduler tuned settings
# - deadline generally recommended for databases, servers, and SSDs,
#   and for more deterministic latency
# - note that read_expire is a key tuning parameter here
# - the following is recommended by DRBD user guide
#     front_merges:    0 (from 1)
#     read_expire:   150 (from 500)
#     write_expire: 1500 (from 5000)
#
# 'noop' io scheduler for variants of HW-RAID.
# - RAID controller will do its own separate scheduling
#
# Overall:
# - We prefer to guarantee latency more than fairness for all platform services,
#   especially under extreme read and write load, e.g, when creating/deleting
#   multiple heat stacks, or running disk intensive operations.

ACTION=="add|change", SUBSYSTEM=="block", KERNEL=="sd[a-z]", ATTR{queue/scheduler}="deadline"
ACTION=="add|change", SUBSYSTEM=="block", KERNEL=="sd[a-z]", ATTR{queue/iosched/front_merges}="0"
ACTION=="add|change", SUBSYSTEM=="block", KERNEL=="sd[a-z]", ATTR{queue/iosched/read_expire}="150"
ACTION=="add|change", SUBSYSTEM=="block", KERNEL=="sd[a-z]", ATTR{queue/iosched/write_expire}="1500"

# Set noop io scheduler for variants of HW-RAID.
# HP ProLiant DL360p Gen8; HP ProLiant DL380p Gen8
ACTION=="add|change", SUBSYSTEM=="block", KERNEL=="sd[a-z]", ATTRS{raid_level}=="*RAID*", ATTR{queue/scheduler}="noop"