KVM and iSCSI

Several technologies are involved in the use of iSCSI:

• Device Mapper (DM) is a framework to access Linux block devices
• iSCSI is an IP protocol to access data storage facilities via ethernet
• Multipath is a fault-tolerance and performance-enhancement technique
• Linux Volume Manager (LVM) is an implementation of Linux logical volume management
• KVM is the virtualization infrastructure that uses iSCSI

Picture 1 delivers an overview over the stack of storage technologies that are used on a KVM host. The information was derived from a host named 'kvm55'. Unless otherwise stated all code examples in this chapter are derived from this host and are compatible with the picture. Picture 1: Overview over devices affected by iSCSI

Please note:
The numbering of DM devices can change by reboot or during host use. Therefore it is essential to check DM device numbers before any DM access. Never rely in information gained quite a while ago.

This content is divided into the following sections:

1. iSCSI basics
2. First connection to iSCSI targets
3. Connecting to configured iSCSI targets
4. Fix iSCSI login errors
5. Multipath
6. LVM devices
7. DM devices
8. Log out of iSCSI targets

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