iSCSI block storage – overview of what it is and why we need it

There are a number of things you need to know about block storage and, in this case, iSCSI. It is a storage area network (SAN) protocol that allows for devices or parts of devices to be seen as block storage by an end device. SAN is how iSCSI connects to the network and gives the ability to provide network logical unit numbers (LUNs). This allows systems to use these block devices as if they were physical hard drives in the system that they can boot from, save files to, or use like any hard drive that you have in your normal computer. With this in mind, we have to take a few things into account.

First, you have to ensure that your network can handle the connectivity without congestion as this will cause your systems to slow down and possibly lag behind what you are doing, causing users to become frustrated. Knowing this, you have to plan out your SAN extremely well and properly network out your block storage onto a normally non-encrypted network setup that meets the minimum speeds of 10 GB but can go much higher in a lot of cases. This allows smooth usage of your storage without the headaches you will run into as a system administrator. If you were to put this on the same network as your LAN traffic and expect your streaming (don’t do this while at work!) users are watching videos while trying to also do their jobs from a machine that is hosted from a SAN iSCSI block storage device. Other things to keep in mind are you need to ensure proper firewalld syntax is utilized and SELinux protocols are followed to allow connectivity at startup or you will have a giant paperweight without much happening.

There are some main items you have to take into account when you are looking at iSCSI using targetcli, and I will get to more details about targetcli as that is the toolset we will utilize to allow us to use iSCSI in our RHEL 8.1 environment. The main things you need to know are the initiator, target, Portal, LUN, Access Control List (ACL), and Target Portal Group (TPG). These items make up iSCSI storage and lead to a lot of misconceptions. Let’s test your knowledge before we dig deeper into the systems and how they work together to provide block storage over the network to remote servers.

Testing your knowledge

Answer the following questions:

1. What is an iSCSI storage source on an iSCSI server?
   1. Target
   2. LUN
   3. iSCSI Qualified Name (IQN)
   4. ACL
2. What is a unique worldwide name used to identify both initiators and targets?
   1. Target
   2. LUN
   3. IQN
   4. ACL
3. An iSCSI client that is typically software-based is known as a:
   1. TPG
   2. Portal
   3. IQN
   4. Initiator
4. Which of the following is an access restriction using the IQN?
   1. Target
   2. LUN
   3. IQN
   4. ACL
5. What is the most commonly used software for setting up RHEL 8.1 iSCSI block storage?
   1. firewalld
   2. SELinux
   3. targetcli
   4. networkd
6. Which service or port do you need to allow for iSCSI to work through your firewall?
   1. iSCSI-target
   2. 3260/UDP
   3. iSCSI
   4. targetcli
7. What includes the named item 2020-06.com.mcleroy.www?
   1. Target
   2. LUN
   3. IQN
   4. ACL
8. Which system do you need to enable to ensure iSCSI will start at boot?
   1. firewalld
   2. Target
   3. targetcli
   4. networkd

Answers:

1. A. Target
2. C. IQN
3. D. Initiator
4. D. ACL
5. C. targetcli
6. A.iSCSI-target
7. C. IQN
8. B. Target