First of all they are shares. I was also talking about SMB and NFS. I forgot to mention SMB
The most basic share that can be created on Synology is SMB, works both on windows and mac. However ISCSI takes this a step further and basically have "less" restriction
* of managing the way for a stable and more open connection:
(I spent, I am not kidding about this. I spent 12hours in dis-belief because both share I had was on the same NAS. SMB and ISCSI.....long story, but iSCSI is a big step up...The background of the music is another dimension!)
To setup ISCSI there are two points. Target and a Initiator. Target is the NAS/Fileserver and Initiator is the streamer who wants to connect. The Initiator basically wants to connect to the share on fileserver.
Depending on what system you are using, Synology has SAN manager where this is setup. After it has been setup you can only access this "target" by the streamer/client with: iSCSI Initiator.
A connection look like any other drive like "C:" - System. However it handles DATA/packages differently
Example of my chain:
NAS(Chrome browser, Games, Audio files,) -> RJ45 -> Cisco switch -> SFP/Fiber -> Cisco switch -> Streamer/Source.
I think there are some processing of the data stream sent to the switches that benefits to the sound. This processing does not happen with SMB/NFS. Other differences is that you can not move executable software like Chrome to SMB share and NFS if I remember correctly. ISCSI is completely open to this. That is why it is so popular and most used for VMs.
* I have setup this ISCSI on the LAN side without any restriction= credential/authenticatio. Straight open to the initiator which is my streamer.
I have setup mine with NOT multiple host. Only single!