Probably the most popular configuration to present VMware vSphere Datastores is to leverage the iSCSI protocol as Block Level. The alternative of course would be the NFS protocol. How difficult is to provision iSCSI targets for applications like VMware to use? Luckily a very simple process especially with a Synology DS620Slim iSCSI targets. The process is completely wizard driven and requires only a few inputs.
Creating Synology DS620Slim iSCSI targets requires at least a Volume sitting on a Storage Pool created on the Synology NAS. This article is a follow up and part of a series dedicated to the Synology DS620Slim. Pretty much same steps are applicable to other models shipping with a similar version of the DSM software (Synology Disk Station Manager). The process is pretty simple and all it requires is to specify the name of the iSCSI LUN Targets where the iSCSI initiators will connect to and consume the storage. Initiators can be VMware vSphere Hosts (stand alone or managed by a vCenter/VCSA) as well as stand alone operating systems with access to “shared storage”. The typical example is the Cluster configuration where the nodes participating to the configuration access the same storage. Of course that storage needs to be formatted with a cluster aware file system and the nodes control access to the storage via software.
In this case these iSCSI targets will serve as VMware datastores. These will be formatted with VMFS file system (VMware native) and will be shared across different VMware Hosts in the Data Center.
Synology DS620Slim iSCSI Target setup
From the main Synology NAS Desktop the Start > iSCSI Manager is the utility to manage the Synology DS620slim iSCSI targets. This also provides an overview of the main events, total targets and LUNs.
In the Targets section the option to start the wizard and create a new Synology DS620slim iSCSI Target. The IQN is automatically generated and represents the address where the iSCSI initiators will connect to. By default the iSCSI protocol doesn’t have encryption for the data traffic and all Targets are visible as soon as initiators have access to the iSCSI Portal. The iSCSI Portal is running on the iSCSI Server. The Synology NAS in this case. It is also possible to allow access only to specific initiators. The CHAP (Challenge Authentication Protocol) can be enforced two ways and provides access only to when providing username and password.
Since this is the first iSCSI LUN, next step is to create one.
This is where the Synology DS620slim iSCSI configuration offers interesting options. A part from the capacity that can be increased at a later stage if required, when choosing Thin Allocation there are other interesting options useful when serving VMware Datastores and Windows based initiators. Rather than processing these actions on the Hosts, the Synology storage run these directly:
- Hardware Assisted Zeroing
- Hardware Assisted Locking
- Hardware Assisted Data Transfer (Microsoft ODX)
- Space Reclamation
A final screen in the wizard to review and confirm settings.
A few moments later and the first Synology DS620slim iSCSI Target is created and ready to use.
When browsing the LUN section it shows the associated LUN to the created iSCSI target. Next step is to let the iSCSI initiator to connect to the Synology Server IP Address on port 3260. This is the default iSCSI Portal port. Once the connection is tested successful it is recommended to restrict access only to the intended initiators or clients with CHAP credentials.
When connecting multiple initiators, for example multiple VMware vSphere Hosts on the same shared storage, it is important to enable:
- Multiple Sessions: allows multiple initiator to share access same storage
- Masking with Read/Write: allows for reading/writing data directly to block storage
Both options are available in the Target > Action > Edit option.