UEK-Specific Optimizations

# Create sysctl configuration
sudo tee /etc/sysctl.d/99-iscsi-uek.conf > /dev/null <<'EOF'
# Network performance (UEK-optimized)
net.core.netdev_max_backlog = 10000
net.core.rmem_max = 268435456
net.core.wmem_max = 268435456
net.ipv4.tcp_rmem = 4096 87380 134217728
net.ipv4.tcp_wmem = 4096 65536 134217728

# Connection tracking
net.netfilter.nf_conntrack_max = 2097152

# Low latency
net.ipv4.tcp_low_latency = 1

# VM tuning for storage
vm.dirty_ratio = 10
vm.dirty_background_ratio = 5
vm.swappiness = 10

# UEK-specific optimizations
kernel.numa_balancing = 0

# ARP settings for same-subnet multipath (CRITICAL)
# Prevents ARP responses on wrong interface when multiple NICs share same subnet
# See: Network Concepts documentation for detailed explanation
net.ipv4.conf.all.arp_ignore = 2
net.ipv4.conf.default.arp_ignore = 2
net.ipv4.conf.all.arp_announce = 2
net.ipv4.conf.default.arp_announce = 2
# Interface-specific (adjust interface names as needed)
net.ipv4.conf.ens1f0.arp_ignore = 2
net.ipv4.conf.ens1f1.arp_ignore = 2
net.ipv4.conf.ens1f0.arp_announce = 2
net.ipv4.conf.ens1f1.arp_announce = 2
EOF

# Apply settings
sudo sysctl -p /etc/sysctl.d/99-iscsi-uek.conf

# Create udev rule
sudo tee /etc/udev/rules.d/99-iscsi-scheduler-uek.rules > /dev/null <<'EOF'
# Set I/O scheduler for iSCSI devices (SSD/Flash)
ACTION=="add|change", KERNEL=="sd[a-z]", ATTR{queue/rotational}=="0", ATTR{queue/scheduler}="none"

# Set queue depth (UEK supports higher values, adjust vendor to match your storage)
ACTION=="add|change", KERNEL=="sd[a-z]", ATTR{device/vendor}=="VENDOR*", ATTR{device/queue_depth}="256"

# Set read-ahead (adjust vendor to match your storage)
ACTION=="add|change", KERNEL=="sd[a-z]", ATTR{device/vendor}=="VENDOR*", ATTR{bdi/read_ahead_kb}="128"

# Enable write cache (adjust vendor to match your storage)
ACTION=="add|change", KERNEL=="sd[a-z]", ATTR{device/vendor}=="VENDOR*", ATTR{queue/write_cache}="write back"
EOF

# Reload udev rules
sudo udevadm control --reload-rules
sudo udevadm trigger