Replace system free-RAM warning with ARC headroom check
The memory warning used plain system-wide 'free' RAM (via free -g), a carryover from before this script was ZFS-specific. ZFS ARC deliberately consumes most otherwise-unused RAM, so 'free' being low is normal and not a meaningful signal — it fired a false alarm on 2026-07-05 (free 5.8Gi, but available a healthy 45Gi). Replaced ZFS_REPORT_FREE_WARN_GB with ZFS_REPORT_ARC_FREE_WARN_GB: warns when ARC headroom (ARC_MAX - ARC_CURRENT) drops below threshold, which is what actually indicates ARC is running out of room to grow. Available RAM check is unchanged — it's a legitimate system-pressure signal on its own.
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Gmer4Lfe
@@ -1311,7 +1311,7 @@
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# Weekly ZFS pool health and memory diagnostic report — informational only.
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ZFS_REPORT_LOG="/var/log/zfs-weekly-health.log"
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ZFS_REPORT_ARC_WARN_PCT=90 # warn if ARC using more than this % of its max
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ZFS_REPORT_FREE_WARN_GB=10 # warn if less than this GB free RAM
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ZFS_REPORT_ARC_FREE_WARN_GB=10 # warn if ARC headroom (max - current) drops below this GB
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ZFS_REPORT_AVAIL_WARN_GB=20 # warn if less than this GB available on ZFS pool
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ZFS_REPORT_DOCKER_TOP=10 # how many top Docker containers to show by memory
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# Pool ignore list defined per host in host*.conf — pool names are server-specific:
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@@ -33,6 +33,14 @@
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# available, Docker not responding — those sections skip, the rest still run.
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# A partial report is more useful than no report.
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#
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# ARC Headroom, Not System Free RAM
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# ZFS ARC deliberately grows to use most of the RAM the system isn't otherwise
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# using — that's the point of a page cache. System-wide "free" RAM being low is
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# therefore normal and not a signal of anything, so the memory warning is based
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# on ARC headroom (ARC_MAX - ARC_CURRENT) instead — how much room ARC itself has
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# left before it hits its configured ceiling. "Available" RAM (which accounts for
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# reclaimable cache) is still checked separately as a true system-pressure signal.
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#
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# ==============================================================================================
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# OPERATIONAL MODEL
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# ==============================================================================================
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@@ -43,10 +51,10 @@
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# ZFS_REPORT_IGNORE_POOLS excluded from the report
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# (still fully monitored by unRAID — report-only exclusion).
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# ARC statistics — current ARC vs max, metadata pressure, hit rate.
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# Warns if ARC utilisation exceeds ZFS_REPORT_ARC_WARN_PCT.
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# Memory status — total, free, available RAM.
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# Warns if free < ZFS_REPORT_FREE_WARN_GB or
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# available < ZFS_REPORT_AVAIL_WARN_GB.
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# Warns if ARC utilisation exceeds ZFS_REPORT_ARC_WARN_PCT, or if
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# ARC headroom (max - current) drops below ZFS_REPORT_ARC_FREE_WARN_GB.
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# Memory status — total, free, available RAM (informational only — see note below).
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# Warns if available < ZFS_REPORT_AVAIL_WARN_GB.
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# Docker memory — top ZFS_REPORT_DOCKER_TOP containers by memory usage.
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# Useful for spotting containers approaching watchdog limits.
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# Kernel pressure — vmstat snapshot (3 samples).
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@@ -102,8 +110,8 @@
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# ZFS_REPORT_ARC_WARN_PCT
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# Warn if ARC is using more than this percentage of its configured max. (default: 90)
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#
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# ZFS_REPORT_FREE_WARN_GB
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# Warn if free RAM is below this threshold in GB. (default: 10)
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# ZFS_REPORT_ARC_FREE_WARN_GB
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# Warn if ARC headroom (ARC_MAX - ARC_CURRENT) drops below this many GB. (default: 10)
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#
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# ZFS_REPORT_AVAIL_WARN_GB
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# Warn if available RAM is below this threshold in GB. (default: 20)
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@@ -159,7 +167,7 @@ done
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log "Identity: $MY_ID ($LOCAL_SERVER_NAME)"
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log "Ignoring pools: ${ZFS_REPORT_IGNORE_POOLS[*]:-none}"
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log "$ICON_GEAR Config: arc-warn=${ZFS_REPORT_ARC_WARN_PCT}% free-warn=${ZFS_REPORT_FREE_WARN_GB}GB avail-warn=${ZFS_REPORT_AVAIL_WARN_GB}GB docker-top=${ZFS_REPORT_DOCKER_TOP}"
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log "$ICON_GEAR Config: arc-warn=${ZFS_REPORT_ARC_WARN_PCT}% arc-free-warn=${ZFS_REPORT_ARC_FREE_WARN_GB}GB avail-warn=${ZFS_REPORT_AVAIL_WARN_GB}GB docker-top=${ZFS_REPORT_DOCKER_TOP}"
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# Tee output to log file unless dry run
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if [[ "$DRY_RUN" == false ]]; then
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@@ -178,7 +186,7 @@ if [[ "$SHOW_STATUS" == true ]]; then
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echo "$ICON_HOST Identity: $MY_ID ($LOCAL_SERVER_NAME)"
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echo "$ICON_ZFS Log file: $ZFS_REPORT_LOG"
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echo "$ICON_ZFS ARC warn: ${ZFS_REPORT_ARC_WARN_PCT}%"
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echo "$ICON_MEM Free RAM warn: ${ZFS_REPORT_FREE_WARN_GB}GB"
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echo "$ICON_ZFS ARC free warn: ${ZFS_REPORT_ARC_FREE_WARN_GB}GB"
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echo "$ICON_MEM Avail warn: ${ZFS_REPORT_AVAIL_WARN_GB}GB"
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echo "$ICON_CONTAINERS Docker top: $ZFS_REPORT_DOCKER_TOP"
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echo "$ICON_ZFS Ignore pools: ${ZFS_REPORT_IGNORE_POOLS[*]:-none}"
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@@ -266,11 +274,13 @@ else
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ARC_META_GB=$(bytes_to_gb "$ARC_META_USED" 1)
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ARC_PCT=$(awk "BEGIN {printf \"%.1f\", $ARC_SIZE * 100 / $ARC_MAX}")
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ARC_PCT_INT=$(printf "%.0f" "$ARC_PCT")
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ARC_FREE_GB=$(awk "BEGIN {printf \"%d\", ($ARC_MAX - $ARC_SIZE) / 1073741824}")
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echo " $ICON_ZFS ARC Max: ${ARC_MAX_GB}GB"
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echo " $ICON_ZFS ARC Current: ${ARC_CUR_GB}GB"
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echo " $ICON_ZFS ARC Meta Used: ${ARC_META_GB}GB"
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echo " $ICON_ZFS ARC Utilization: ${ARC_PCT}%"
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echo " $ICON_ZFS ARC Free: ${ARC_FREE_GB}GB"
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if [[ "$ARC_PCT_INT" -ge "$ZFS_REPORT_ARC_WARN_PCT" ]]; then
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warn "ARC utilization ${ARC_PCT}% — above ${ZFS_REPORT_ARC_WARN_PCT}% threshold"
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@@ -279,6 +289,13 @@ else
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log "ARC utilization ${ARC_PCT}% — within threshold ✅"
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fi
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if [[ "$ARC_FREE_GB" -lt "$ZFS_REPORT_ARC_FREE_WARN_GB" ]]; then
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warn "ARC free ${ARC_FREE_GB}GB — below ${ZFS_REPORT_ARC_FREE_WARN_GB}GB threshold"
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WARNINGS+=("ARC headroom low: ${ARC_FREE_GB}GB")
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else
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log "ARC free ${ARC_FREE_GB}GB — within threshold ✅"
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fi
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echo ""
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META_MRU_GHOST=$(awk '/^mru_ghost_metadata / {print $3}' \
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/proc/spl/kstat/zfs/arcstats 2>/dev/null || echo 0)
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@@ -302,20 +319,12 @@ echo "━━━ $ICON_MEM Memory Status ━━━"
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FREE_HUMAN=$(free -h | awk '/Mem:/ {print $4}')
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AVAIL_HUMAN=$(free -h | awk '/Mem:/ {print $7}')
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TOTAL_HUMAN=$(free -h | awk '/Mem:/ {print $2}')
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FREE_GB=$(free -g | awk '/Mem:/ {print $4}')
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AVAIL_GB=$(free -g | awk '/Mem:/ {print $7}')
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echo " $ICON_MEM Total RAM: $TOTAL_HUMAN"
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echo " $ICON_MEM Free RAM: $FREE_HUMAN"
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echo " $ICON_MEM Free RAM: $FREE_HUMAN (informational — ARC intentionally uses most of this)"
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echo " $ICON_MEM Available RAM: $AVAIL_HUMAN"
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if [[ "$FREE_GB" -lt "$ZFS_REPORT_FREE_WARN_GB" ]]; then
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warn "Free RAM ${FREE_HUMAN} — below ${ZFS_REPORT_FREE_WARN_GB}GB threshold"
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WARNINGS+=("Low free RAM: ${FREE_HUMAN}")
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else
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log "Free RAM ${FREE_HUMAN} — within threshold ✅"
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fi
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if [[ "$AVAIL_GB" -lt "$ZFS_REPORT_AVAIL_WARN_GB" ]]; then
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warn "Available RAM ${AVAIL_HUMAN} — below ${ZFS_REPORT_AVAIL_WARN_GB}GB threshold"
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WARNINGS+=("Low available RAM: ${AVAIL_HUMAN}")
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