Part 1: Configuring the iSCSI SAN Infrastructure
Our first step will be physically setting up the SAN.
If you already have your SAN infrastructure in place, you can skip this section.
In this article, I am using a Dell MD 3000i iSCSI SAN with dual controllers and using 14 drives for the array plus a hot spare.
Though I am using a specific Dell unit, the concept and configuration here should not be much different for any make or model of iSCSI SAN.
The back of the SAN has a total of 6 network ports since there are two modules in it.
1 Network port used for SAN management on each of the two Storage Processors/ Raid Controller modules
2 Gigabit network ports on each of the two Storage Processors/ Raid Controller modules for iSCSI traffic
Note: You should refer to the configuration manual provided for your model to ensure the best configuration for your unit is utilized.
The goal for the SAN infrastructure is to configure as much failover and load balancing ability as the hardware will support.
In the case of our MD3000i, I will setup each storage processor (raid controller module) with two separate ways in and out of either raid controller module via two independent subnets. In turn, each server/node that will access the SAN for iSCSI storage will dedicate two NIC ports from differing NICs to provide separate routes to the SAN.
When complete each of the two storage processors on the SAN will have a 200.x IP, and a 201.x IP – both connected to separate switches, and each server will have at least two separate network cards each connecting one port to one of the two respective dedicated gigabit switches and serve static IPs of 200.x and 201.x respectively.
Ensure that the switches you use support jumbo frames, and that you enable it (MTU 9000). We will be using jumbo frames on the iSCSI traffic for better performance. (Jumbo frames is not mandatory but recommended)
With this configuration, a switch could fail, a storage processor could fail, a NIC could fail, a cable could fail and any of these failures would not drop the server’s connection to the SAN once the initiator is configured correctly. In fact, you could have all of these components fail on one of the two subnets and you would still be up and running.
Though a full failover and balanced configuration like this is not a requirement for a SAN, nor is it needed to setup a cluster, it is very strongly recommended. You could optionally setup an iSCSI configuration that uses only one controller module, switch, and subnet. More so, if you were only ever planning on connecting two servers to your SAN you could even omit the switch and directly connect each to one of the two ports on a single controller module. This would still support a cluster. These options cost a lot less, and are simpler to setup but you will lose both failover, and performance.
Logical configuration
Now that your SAN is powered up and the management ports are plugged in to the LAN, you will be able to configure your SAN.
The process here will vary by brand and by model. For our MD3000i, we install the Modular Disk storage manager software on our chosen management station, and connect to the SAN.
Once connected, feel free to configure the general settings as you wish, such as notifications, time, management port static IPs etc. For this article, I will just stick to the specifics
important to our goal here.
1) Set Static IPs for your 4 iSCSI ports on the SAN
a. From the MDSM, go to the iSCSI tab and select the option called ‘Configure iSCSI Ports’
b. Set the desired static IPs on each of the 4 Raid controller module ports and enable ICMP responses.
Remember, we want each module to have an IP for each of the two subnets. I will use the following;
192.168.200.1 Module 0, Port 0 192.168.200.2 Module 1, Port 0 192.168.201.1 Module 0, Port 1 192.168.201.2 Module 1, Port 1 c. Set Jumbo frames on each of the four ports.
From the Configure Host ports page, click on the ‘Advanced Host Port Settings’ button
d. Check the noted box to enable jumbo frames and set the MTU size to 9000 2) Create two Virtual Disks
The reason you want to create two virtual disks for your cluster is that the MD3000i uses Asymmetrical processing. Each Virtual disk has a selected owner, and iSCSI traffic will pass through the owner module only. By creating two virtual disks, you can assign each a different module as owner and help balance out the load across both storage modules through monitoring and adjustments in provisioning later on. Your iSCSI SAN may not have this limitation, unfortunately mine does. Note this is an optional step regardless, but it is recommended for better performance.
a. From the MDSM go to the Configure tab b. Select ‘Create Disk Groups and Virtual Disks’
c. Expand your Disk Group, select Free Capacity and click Next Create a Disk Group first if you had not already done so.
I chose to create just one group that used all the drives (most possible spindles)
d. Select the size you wish to make your first Virtual Disk e. Give your VD a descriptive name and click next
f. Choose to Map later and click finish
g. Repeat this process to create your second Virtual Disk
h. Once complete, you will have two different Virtual Disks that can each be assigned a different module as their owner
3) The SAN is now ready for the hosts to connect to it. We now need to install and configure our servers for iSCSI before we can grant host access and map the Virtual disks.
