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#!/usr/bin/env bash
# raid.sh - Pure RAID-level logic (testable, no I/O).
# Source after common.sh.
#############################
# Valid-level enumeration
#############################
# Print valid RAID levels for a given disk count, one per line.
# Count <2: nothing printed (single disk = no RAID).
# Count 2: mirror, stripe
# Count 3+: + raidz1
# Count 4+: + raidz2
# Count 5+: + raidz3
raid_valid_levels_for_count() {
local count=$1
[[ $count -lt 2 ]] && return 0
echo mirror
echo stripe
[[ $count -ge 3 ]] && echo raidz1
[[ $count -ge 4 ]] && echo raidz2
[[ $count -ge 5 ]] && echo raidz3
return 0
}
# Return 0 if level is valid for the given disk count, 1 otherwise.
# Empty level with count 1 is valid (no RAID).
raid_is_valid() {
local level=$1 count=$2
if [[ $count -le 1 ]]; then
[[ -z "$level" ]]
return
fi
raid_valid_levels_for_count "$count" | grep -qxF "$level"
}
#############################
# Usable-space computation
#############################
# Print usable bytes for a level given disk count, smallest-disk bytes,
# and total bytes across all disks. Writes nothing and returns 1 for
# unknown levels.
#
# Usage: raid_usable_bytes LEVEL COUNT SMALLEST_BYTES TOTAL_BYTES
raid_usable_bytes() {
local level=$1 count=$2 smallest=$3 total=$4
case "$level" in
mirror) echo "$smallest" ;;
stripe) echo "$total" ;;
raidz1) echo $(( (count - 1) * smallest )) ;;
raidz2) echo $(( (count - 2) * smallest )) ;;
raidz3) echo $(( (count - 3) * smallest )) ;;
*) return 1 ;;
esac
}
# Print fault-tolerance (max number of disks that can fail) for a level
# at the given disk count. Unknown level → return 1.
raid_fault_tolerance() {
local level=$1 count=$2
case "$level" in
mirror) echo $(( count - 1 )) ;;
stripe) echo 0 ;;
raidz1) echo 1 ;;
raidz2) echo 2 ;;
raidz3) echo 3 ;;
*) return 1 ;;
esac
}
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