Pre‑Deployment OS Tuning for GBase 8a: ulimit, Kernel, Disk, and Network

*    soft    nofile     655360
*    hard    nofile     655360
*    soft    nproc      655360
*    hard    nproc      655360
*    soft    core       unlimited
*    hard    core       unlimited

DefaultLimitNOFILE=655360
DefaultLimitNPROC=655360
DefaultLimitCORE=infinity

su - gbase
ulimit -n   # must show 655360
ulimit -u   # must show 655360

# Confirm the running gnode process limits
PID=$(pgrep -f gbase | head -1)
cat /proc/$PID/limits | grep -E "Max open files|Max processes"

# Virtual memory
vm.swappiness = 1
vm.dirty_ratio = 10
vm.dirty_background_ratio = 5

# HugePages (gnode memory / 2MB)
vm.nr_hugepages = 32768

# File system
fs.file-max = 6553560

# Network stack
net.core.rmem_max = 134217728
net.core.wmem_max = 134217728
net.core.rmem_default = 25165824
net.core.wmem_default = 25165824
net.ipv4.tcp_rmem = 4096 87380 134217728
net.ipv4.tcp_wmem = 4096 87380 134217728
net.core.netdev_max_backlog = 250000
net.core.somaxconn = 65535
net.ipv4.tcp_fin_timeout = 15
net.ipv4.tcp_tw_reuse = 1
net.ipv4.ip_local_port_range = 10000 65000
net.ipv4.tcp_keepalive_time = 300
net.ipv4.tcp_keepalive_intvl = 30
net.ipv4.tcp_keepalive_probes = 5

# Shared memory
kernel.shmmax = 68719476736
kernel.shmall = 4294967296
kernel.sem = 250 32000 100 128

echo never > /sys/kernel/mm/transparent_hugepage/enabled
echo never > /sys/kernel/mm/transparent_hugepage/defrag
# Persist in /etc/rc.d/rc.local
# Verify: expected output includes [never]
cat /sys/kernel/mm/transparent_hugepage/enabled

/dev/sdb  /opt/gbase  xfs  defaults,noatime,nodiratime  0  0

# Bandwidth test between nodes (10GbE should reach >9 Gbps)
iperf3 -c 10.168.10.27 -t 30 -P 4

# Distribute NIC interrupts
systemctl enable irqbalance && systemctl start irqbalance

#!/bin/bash
echo "===== Open Files ====="
su - gbase -c "ulimit -n" 2>/dev/null
echo "System file-max: $(cat /proc/sys/fs/file-max)"

echo "===== THP ====="
cat /sys/kernel/mm/transparent_hugepage/enabled

echo "===== Swap ====="
free -h && cat /proc/sys/vm/swappiness

echo "===== I/O Scheduler ====="
for disk in $(ls /sys/block/ | grep -E '^sd|^nvme'); do
    echo "$disk: $(cat /sys/block/$disk/queue/scheduler 2>/dev/null)"
done

echo "===== Network ====="
sysctl net.core.rmem_max net.core.wmem_max net.ipv4.tcp_tw_reuse

echo "===== Time Sync ====="
timedatectl status | grep -E "synchronized|NTP"

echo "===== SELinux ====="
sestatus 2>/dev/null || echo "sestatus not available"

echo "===== Firewall ====="
systemctl status firewalld 2>/dev/null | grep Active