iSCSI LUN

iSCSI is a storage networking service that facilitates transferring data over local networks or long distances. By mapping iSCSI LUNs to iSCSI Targets, clients may access storage spaces as if they were local disks. An iSCSI LUN (logical unit number) can be mapped to one or multiple iSCSI Targets to provide iSCSI storage services.

Synology NAS currently supports the following types of iSCSI LUNs:

iSCSI LUN (Regular Files):This type of iSCSI LUN is created by designating a portion of a volume. It may be later expanded as needed. This type of iSCSI LUN provides the flexibility of dynamic capacity management with Thin Provisioning, VMware VAAI hardware acceleration support, LUN snapshot and LUN clone.
iSCSI LUN (Block-Level): This type of iSCSI LUN is created on a RAID Group and provides flexibility of dynamic capacity management in addition to optimized access performance. You can expand this type of iSCSI LUN later using unallocated space on the RAID Group. Please refer to the RAID Group page for more information.

Note: iSCSI LUNs with advanced LUN features are only available on EXT4 file system.

Term explanations:

Thin Provisioning: Thin Provisioning is a method for optimizing storage utilization by allocating storage space in a dynamic and on-demand manner. This setting is only available for iSCSI LUN (regular files).
VMware VAAI: The VMware vStorage APIs for Array Integration (VAAI) can offload the work of the standard operations on virtual storage arrays to the iSCSI device in the VMware vSphere environment and optimize the storage performance.
iSCSI Target Mapping: To map the iSCSI LUN to one or multiple iSCSI Targets.

To create an iSCSI LUN:

Click Create.
Select the iSCSI LUN type you wish to create.
Follow the wizard to complete the process.

Note: Advanced LUN features can only be enabled during initial iSCSI LUN creation. This setting cannot be changed afterwards.

To remove an iSCSI LUN:

When removing an iSCSI LUN, all data on the iSCSI LUN will be deleted. Connections between the iSCSI LUN and any mapped iSCSI Targets will be lost also.

Select the iSCSI LUN you want to remove.
Click Remove button and follow the wizard to complete the process.

Note: Deleting VAAI LUNs on the RackStation does not free up disk space immediately. Data is moved to a system reserved folder called @EP_trash and deleted piece by piece. For example, if a 100 GB VAAI LUN is deleted from the RackStation, it might take approximately 15-20 minutes to free up the 100 GB of space on the disk volume.

To edit an iSCSI LUN:

Select the iSCSI LUN you want to edit.
Click Edit.
Edit the desired properties.
Click OK to save the settings.

To take an iSCSI LUN snapshot:

A snapshot of an iSCSI LUN is a point-in-time, read-only copy of an iSCSI LUN.

Select the iSCSI LUN of which you want to take snapshots.
Click Snapshot and choose Take a Snapshot.
Enter description for the snapshot and click OK.

To restore an iSCSI LUN:

Select a point-in-time snapshot to restore the data on an iSCSI LUN.

Select the iSCSI LUN you want to restore.
Click Snapshot and choose Snapshot Manager.
Select a snapshot to which you want to restore and click Restore.

To clone an iSCSI LUN:

Make a writable copy of an iSCSI LUN or an iSCSI LUN snapshot.

Select an iSCSI LUN from the left panel or an iSCSI LUN snapshot from Snapshot Manager.
Click Clone.
Follow the instructions to complete the process.

Note:

LUN snapshot/restore and clone functions are only available on iSCSI LUNs with advanced LUN features.
If you took a snapshot or created a clone, and the status turned out to be Abnormal/Crashed, please delete this snapshot/clone and create another one.
If there are any connected iSCSI sessions associated with the LUN you are about to clone/restore or take snapshots of, to avoid possible data inconsistency, you must log off from the initiators and stop all related applications before proceeding.
All changes to a LUN after a snapshot was created will be lost when you restore LUN to this snapshot.
If the status of an iSCSI LUN changes to Unavailable, it means that some data-related errors occurred while accessing iSCSI LUN. In order to avoid severe data loss on your system, this iSCSI LUN will be temporarily inaccessible. Please contact Synology for support as soon as possible.