Group Scoped iSCSI Target

The array OS 5.1.x and later supports iSCSI Group Scoped Target (GST) on iSCSI arrays. GST reduces the number of individual host connections you need to configure and manage, which saves you time.

For example, with Volume Scoped Target (VST), if you need to connect four iSCSI volumes to the host, you would need to connect each target to the host individually. With GST, if you want to connect those same four volumes, you only need to connect to the one target.

NOTE: When you perform a new installation of the array 5.1.x or later, your default target will use GST. If you upgrade to 5.1.x or later, your default target will continue to use VST.
The benefits of GST over VST include:
  • Full mesh connections enable optimal performance and resiliency.
  • LUNs can be added to or removed from the host at the array level, so there is no need connect them to or disconnect them from the host one at a time.
  • Volumes under GST are managed using Access Control List (ACL) records, similar to Fibre Channel (FC) targets.
  • With GST, you connect the single group scoped target, and volumes can be added or removed through the array GUI.
  • GST is supported in environments where Synchronous Replication is enabled, but VST is not. A synchronously replicated volume collection exposes the GST ACL information to the downstream pool.
    NOTE: If the group leader array goes down and HPE Peer Persistence (also referred to as synchronous replication and Automatic Switchover) is not enabled, the host will lose access to all GST LUNs. Before you perform a manual takeover, you should take down the cluster. You can bring the cluster up again after the takeover completes.
Table 1. Comparison of VST and GST
  Volume Scoped Target Group Scoped Target
Target IQN Contains the volume name Contains the group name
Number of IQNs per target One per volume One per group
SendTargets response Contains discovery IP as portal One target per data IP, same IQN, different portal
Open Access Allowed, can use \* to add ACLs to initiator group for a volume Disallowed, must use an actual initiator group
Connections Host connects to discovery IP and is redirected to the target Host issues sendtargets to the discovery IP, but connections are made using the data IP.
GST volumes have these characteristics:
  • The IQN is the name of the array group and its ID, and is the same for all GST volumes.
  • Each volume has multiple LUN numbers.
  • Instead of logging in to each volume, the hosts log in to the group, so the number of connections can be substantially decreased.
  • Access is managed by adding or removing ACL records to or from the CHAP user, similar to FC.
NOTE: SMI-S does not support GTS.
In contrast VST volumes have these characteristics:
  • Each volume has a unique iSCSI Qualified Name (IQN).
  • The volume name is part of the IQN.
  • Each volume is LUN-0.
  • Hosts log in to each volume as separate entities, which affects your ability to scale.
  • If CHAP authentication is desired, each volume must be configured for CHAP access using the host IQN or an IP to multiple ACLs.