iSCSI on Oracle Linux - Quick Start Guide

Important:

Vendor Documentation Priority: This guide is for reference only. Always consult official vendor documentation for your distribution. Test thoroughly in a lab environment before production use.

Note: For detailed explanations, alternative configurations, and troubleshooting: See iSCSI Best Practices

Prerequisites:

Oracle Linux 8.x or 9.x with UEK R7 (5.15+) recommended
FlashArray configured with portal IPs and target IQN
Dedicated storage network interfaces
Root or sudo access

Note:

New to iSCSI? See the Storage Terminology Glossary

Warning:

If using multiple interfaces on the same subnet, configure ARP settings. See ARP Configuration.

Install Packages:

sudo dnf install -y iscsi-initiator-utils device-mapper-multipath
sudo systemctl enable --now iscsid multipathd

Configure Network Interfaces:

# First storage interface
sudo nmcli connection add type ethernet \
    con-name storage-1 \
    ifname <INTERFACE_NAME_1> \
    ipv4.method manual \
    ipv4.addresses <HOST_IP_1>/<CIDR> \
    ipv4.never-default yes \
    802-3-ethernet.mtu 9000 \
    connection.autoconnect yes

# Second storage interface
sudo nmcli connection add type ethernet \
    con-name storage-2 \
    ifname <INTERFACE_NAME_2> \
    ipv4.method manual \
    ipv4.addresses <HOST_IP_2>/<CIDR> \
    ipv4.never-default yes \
    802-3-ethernet.mtu 9000 \
    connection.autoconnect yes

# Activate
sudo nmcli connection up storage-1
sudo nmcli connection up storage-2

Warning:

If both interfaces are on the same subnet, configure ARP settings. See ARP Configuration.

Configure Firewall:

Add storage interfaces to trusted zone (recommended for dedicated storage networks):

# Check if firewalld is running (skip if not installed, e.g., minimal/cloud images)
if systemctl is-active --quiet firewalld; then
    sudo firewall-cmd --permanent --zone=trusted --add-interface=<INTERFACE_NAME_1>
    sudo firewall-cmd --permanent --zone=trusted --add-interface=<INTERFACE_NAME_2>
    sudo firewall-cmd --reload
else
    echo "firewalld not running - skipping firewall configuration"
fi

Note:

Alternative: For port filtering options, see Best Practices - Firewall Configuration.

Configure iSCSI Initiator:

# View/generate initiator name
cat /etc/iscsi/initiatorname.iscsi

# Set automatic startup
sudo sed -i 's/^node.startup = manual/node.startup = automatic/' /etc/iscsi/iscsid.conf
sudo systemctl restart iscsid

Register this initiator IQN on FlashArray.

Create Interface Bindings:

# Create and bind first interface
sudo iscsiadm -m iface -I iface0 --op=new
sudo iscsiadm -m iface -I iface0 --op=update -n iface.net_ifacename -v <INTERFACE_NAME_1>

# Create and bind second interface
sudo iscsiadm -m iface -I iface1 --op=new
sudo iscsiadm -m iface -I iface1 --op=update -n iface.net_ifacename -v <INTERFACE_NAME_2>

Discover and Login:

# Discover targets
sudo iscsiadm -m discovery -t sendtargets -p <PORTAL_IP_1>:3260
sudo iscsiadm -m discovery -t sendtargets -p <PORTAL_IP_2>:3260

# Login via each interface to each portal
sudo iscsiadm -m node -T <TARGET_IQN> -p <PORTAL_IP_1>:3260 -I iface0 --login
sudo iscsiadm -m node -T <TARGET_IQN> -p <PORTAL_IP_2>:3260 -I iface0 --login
sudo iscsiadm -m node -T <TARGET_IQN> -p <PORTAL_IP_1>:3260 -I iface1 --login
sudo iscsiadm -m node -T <TARGET_IQN> -p <PORTAL_IP_2>:3260 -I iface1 --login

# Set automatic login
sudo iscsiadm -m node -T <TARGET_IQN> --op=update -n node.startup -v automatic

# Verify sessions
sudo iscsiadm -m session

Configure Multipath:

Create /etc/multipath.conf:

sudo tee /etc/multipath.conf > /dev/null <<'EOF'
defaults {
    find_multipaths      no
    polling_interval     10
    path_selector        "service-time 0"
    path_grouping_policy group_by_prio
    failback             immediate
    no_path_retry        0
}

# Blacklist local devices and NVMe to prevent dm-multipath management
# NVMe uses native multipath (nvme_core multipath=Y), not dm-multipath
blacklist {
    # Local boot devices (adjust patterns for your environment)
    devnode "^(ram|raw|loop|fd|md|dm-|sr|scd|st)[0-9]*"
    devnode "^sd[a]$"    # Adjust if boot device differs

    # All NVMe devices - use native NVMe multipath instead
    devnode "^nvme"

    # Virtual devices
    devnode "^vd[a-z]"
}

# Add device-specific settings for your storage array
# Default configurations for many storage arrays are included in the multipath package
# Example for a storage array supporting ALUA:
#devices {
#    device {
#        vendor           "VENDOR"
#        product          "PRODUCT"
#        path_selector    "service-time 0"
#        hardware_handler "1 alua"
#        path_grouping_policy group_by_prio
#        prio             alua
#        failback         immediate
#        path_checker     tur
#        fast_io_fail_tmo 10
#        dev_loss_tmo     60
#        no_path_retry    0
#    }
#}
EOF

# Restart multipathd to apply configuration
sudo systemctl restart multipathd

# Verify multipath devices (should only show iSCSI devices)
sudo multipath -ll

Tip:

Why blacklist local and NVMe devices?
- Local devices: Prevents dm-multipath from managing boot drives and local storage
- NVMe devices: NVMe uses native kernel multipath (nvme_core multipath=Y), not dm-multipath. Managing NVMe with dm-multipath causes conflicts and performance issues.
Why find_multipaths no?

This ensures ALL paths to iSCSI storage devices are claimed by multipath immediately, rather than waiting to detect multiple paths. See iSCSI Best Practices for detailed explanation.

Create LVM Storage:

# Find multipath device
sudo multipath -ll
# Example: mpatha

# Create LVM
sudo pvcreate /dev/mapper/mpatha
sudo vgcreate iscsi-storage /dev/mapper/mpatha
sudo lvcreate -L 500G -n data iscsi-storage

# Format and mount (Oracle Linux: XFS recommended)
sudo mkfs.xfs /dev/iscsi-storage/data
sudo mkdir -p /mnt/iscsi-storage
sudo mount /dev/iscsi-storage/data /mnt/iscsi-storage

# Add to fstab
echo '/dev/iscsi-storage/data /mnt/iscsi-storage xfs defaults,_netdev 0 0' | sudo tee -a /etc/fstab

Verify Configuration:

# Check sessions
sudo iscsiadm -m session

# Check multipath
sudo multipath -ll

# Verify storage
df -h | grep iscsi

Note:

Quick Reference

Command	Description
`sudo iscsiadm -m session`	List active iSCSI sessions
`sudo iscsiadm -m discovery -t sendtargets -p <IP>:3260`	Discover targets
`sudo iscsiadm -m node -T <IQN> -p <IP>:3260 --login`	Login to target
`sudo iscsiadm -m node -T <IQN> -p <IP>:3260 --logout`	Logout from target
`sudo multipath -ll`	Show multipath devices

For production deployments, see iSCSI Best Practices for:

Network design and VLAN configuration
Multipath configuration details
Security best practices (SELinux, CHAP, firewall options)
Monitoring
High availability considerations
UEK vs RHCK kernel selection
Ksplice zero-downtime updates

Additional Resources: