Virtual disks can be shared using the iSCSI protocol. iSCSI is used to facilitate data transfers over intranets and manage storage over long distances. The protocol requires identifying the hosts allowed to connect (called remote initiators), the endpoints on the appliance (called local targets) and a LUN (logical unit number) associated to the virtual disk for that connection. At the moment, Syneto Storage can only be configured as a target (other initiators will access its shared data).

The image below presents an overview of the iSCSI sharing mechanism:

Remote initiators and local targets are identified by strings using an iqn, wwn or eui format. See the RFC 3720 for details.

Remote initiators must be part of a  remote initiator group. Local targets can be part of a local target group, but it’s not mandatory. Initiator groups are used for sharing virtual disks to multiple initiators at the same time. Target groups are used to share a virtual disk via multiple targets at the same time.

Note: A target or an initiator cannot be part of multiple groups at the same time.

Sharing virtual disks

These are the steps required to make a virtual disk available to one or more iSCSI initiators:

1. Click on New initiator. Enter its identifier and the group it will belong to (you can also create a new group at this step). Click Add and the new initiator will be added.
   
   

   
   
   

2. If desired, create a local target and associate it to a group (click New target, enter its identifier and group, then click Add). However, creating a local target is not required, as a default local target is created when the machine is installed.
   
   

   
   
   

3. Go to the page Data Management > Folders / Virtual Disks and select the virtual disk you want to make available to the newly created remote initiator group. If you don’t have a virtual disk to share, first create one (see how on Folders and Virtual Disks).
   
   

4. On the iSCSI/FC share tab click on the New iSCSI/FC share button.
   

   
   
   

   Select the initiator group created in step 3 and the target group from step 4. If you have not defined a target group you can make the vdisk through all targets by leaving the All option selected. Finally, choose a logical unit number (LUN) and click Add.

   Note: the LUN number must be unique for the selected initiator group (i.e. one remote initiator group can view only one virtual disk on the same LUN)

5. At this point, the hosts from the remote initiator group can access the virtual disk.
   
   

   
   
   
6. The actions that can be performed on the shares are: toggle the Writeback cache option or delete them.
   Enabling iSCSI writeback cache improves performance by caching your data in memory and flush it on disk at given intervals.

   Warning: this may cause data loss in case of power failure or unfinished iSCSI transactions.

Configuring iSCSI initiators on different platforms

• Windows: Microsoft iSCSI initiator user guide and Connecting Windows 7 iSCSI SAN.

• Linux: Linux iSCSI Quick Start Guide.