Prerequisite

iSCSI Requirements

The following requirements must be fulfilled in order to successfully use the iSCSI protocol with the CSI PowerStore driver:

• Ensure that the necessary iSCSI initiator utilities are installed on each Kubernetes worker node. This typically includes the iscsi-initiator-utils package for RHEL or open-iscsi package for Ubuntu.
• Enable and start the iscsid service on each Kubernetes worker node. This service is responsible for managing the iSCSI initiator. You can enable the service by running the following command on all worker nodes: systemctl enable --now iscsid
• Ensure that the unique initiator name is set in /etc/iscsi/initiatorname.iscsi.
• Ensure that the iSCSI initiators are available on all the nodes where the driver node plugin will be installed.
• Ensure that the unique initiator name is set in /etc/iscsi/initiatorname.iscsi.
• Kubernetes nodes must have network connectivity to an iSCSI port on the PowerStore array that has IP interfaces.
• Ensure that the iSCSI initiators on the nodes are not a part of any existing Host or Host Group on the PowerStore arrays. The driver will create host entries for the iSCSI initiators which adheres to the naming conventions required by the driver.

Refer to the Dell Host Connectivity Guide for more information.

NVMe Requirements

The following requirements must be fulfilled in order to successfully use the NVMe protocols with the CSI PowerStore driver:

• All OpenShift or Kubernetes nodes connecting to Dell storage arrays must use unique host NVMe Qualified Names (NQNs).

• The driver requires the NVMe command-line interface (nvme-cli) to manage the NVMe clients and targets. The NVMe CLI tool is installed in the host using the following command on RPM oriented Linux distributions.

  sudo dnf -y install nvme-cli
  

• Support for NVMe requires native NVMe multipathing to be configured on each worker node in the cluster. Please refer to the Dell Host Connectivity Guide for more details on NVMe multipathing requirements. To determine if the worker nodes are configured for native NVMe multipathing run the following command on each worker node:

  cat /sys/module/nvme_core/parameters/multipath
  

  If the result of the command displays Y then NVMe native multipathing is enabled in the kernel. If the output is N then native NVMe multipating is disabled. Consult the Dell Host Connectivity Guide for Linux to enable native NVMe multipathing.

Configure the IO policy

• The default NVMeTCP native multipathing policy is “numa”. The preferred IO policy for NVMe devices used for PowerStore is round-robin. You can use udev rules to enable the round robin policy on all worker nodes. To view the IO policy you can use the following command:

  nvme list-subsys
  

ACTION=="add|change", SUBSYSTEM=="nvme-subsystem", ATTR{iopolicy}="round-robin"

In order to change the rules on a running kernel you can run the following commands:

/sbin/udevadm control --reload-rules
/sbin/udevadm trigger --type=devices --action=change

Configure the control loss timeout

To reduce the impact of PowerStore non disruptive software upgrades you must set the control loss timeout. This can be done using udev rules on each worker node. More information can be found in the Dell Host Connectivity Guide. To configure the control loss timeout place a config file in /etc/udev/rules.d with the name 72-nvmf-ctrl_loss_tmo.rules with the following contents:

ACTION=="add|change", SUBSYSTEM=="nvme", KERNEL=="nvme*", ATTR{ctrl_loss_tmo}="-1"

/sbin/udevadm control --reload-rules
/sbin/udevadm trigger --type=devices --action=change

Requirements for NVMeTCP

• Modules including the nvme, nvme_core, nvme_fabrics, and nvme_tcp are required for using NVMe over Fabrics using TCP. Load the NVMe and NVMe-OF Modules using the below commands:

  modprobe nvme
  modprobe nvme_tcp
  

  
  
• The NVMe modules may not be available after a node reboot. Loading the modules at startup is recommended.

Requirements for NVMeFC

• NVMeFC Zoning of the Host Bus Adapters (HBAs) to the Fibre Channel port must be done.

Do not load the nvme_tcp module for NVMeFC

1. Configuration steps:

   • Install the Device Mapper Multipathing package on all nodes:

     • dnf install device-mapper-multipath
     • apt install multipath-tools

   • Enable multipathing: mpathconf --enable --with_multipathd y

   • Edit /etc/multipath.conf to enable user_friendly_names and find_multipaths.

   • Ensure the mpathconf command is available on all Kubernetes nodes.

The following is a simple sample multipath.conf file. For a detailed sample, refer Dell Technologies Host Connectivity.

defaults {
	polling_interval 5
	checker_timeout 15
	disable_changed_wwids yes
	find_multipaths no
}
devices {
	device {
		vendor DellEMC
		product PowerStore
		detect_prio "yes"
		path_selector "queue-length 0"

		path_grouping_policy "group_by_prio"
		path_checker tur
		failback immediate
		fast_io_fail_tmo 5
		no_path_retry 3
		rr_min_io_rq 1
		max_sectors_kb 1024
		dev_loss_tmo 10
		hardware_handler "1 alua"
	}
	device {
		vendor .*
		product dellemc-powerstore
		uid_attribute ID_WWN
		prio ana
		failback immediate
		path_grouping_policy "group_by_prio"
		path_checker "none"
		path_selector "queue-length 0"
		detect_prio "yes"
		fast_io_fail_tmo 5
		no_path_retry 3
		rr_min_io_rq 1
		max_sectors_kb 1024
		dev_loss_tmo 10
	}
}

On some distributions the multipathd service for changes to the configuration and dynamically reconfigures itself. If you need to manually trigger a reload you can run the following command: sudo systemctl reload multipathd