Subnet config and switch layout for windows 2012 ISCSI server

Question

I would like to ask about subnet design and switch layout in regards to using a Windows 2012 ISCSI solution. When you guys design subnets for ISCSI configurations do you use one subnet or multiple subnets?  Also do you link the switches together when
designing your ISCSI layouts? These types of things are normally discussed in vendor deployment guides.  However, I have not come across a best practices guide for deploying Server 2012 ISCSI.

Answer 1

I would like to ask about subnet design and switch layout in regards to using a Windows 2012 ISCSI solution. When you guys design subnets for ISCSI configurations do you use one subnet or multiple subnets?  Also do you link the switches together
when designing your ISCSI layouts? These types of things are normally discussed in vendor deployment guides.  However, I have not come across a best practices guide for deploying Server 2012 ISCSI.
For iSCSI you typically create a separate subnets around physical NICs you use for iSCSI traffic (assuming they are used by iSCSI target for MPIO of course). Here are few guides on how to do that (some for Windows Server 2008 R2 but you can ignore that fact
as target itself did not change much and concepts are still the same). See:
Configure iSCSI MPIO on Windows (full)
http://blogs.technet.com/b/migreene/archive/2009/08/29/3277914.aspx
(make sure you have at leas one connection before you try to enable MPIO)
Setting up a Target and Initiator
http://www.server-log.com/blog/2011/7/26/setting-up-an-microsoft-iscsi-target-and-initiator-using-mpi.html
You need however be aware of a couple of facts... 
1) MSFT does not see much future in iSCSI and is replacing it with SMB3 where it can. So if you want to use iSCSI to provide shared storage to your guest VMs you need to use shared VHDX hosted on SMB3 share, see:
Shared VHDX for guest VM Cluster
http://technet.microsoft.com/en-us/library/dn265980.aspx
If you plan to use iSCSI to host CSV and VM images there you again can use SMB3 share, see:
Hyper-V over SMB
http://technet.microsoft.com/en-us/library/jj134187.aspx
That's both simpler to manage (you don't configure anything except teaming for NICs to enable SMB Multichannel and create a shared folder in a few clicks) and faster: MSFT iSCSI target is not cached @ server side while (OK, Hyper-V ovens VMs in a pass-thru
mode but other users typically don't do that). SQL Server is the same as Hyper-V in terms of SMB3 support, Windows clusters support SMB3 share as a witness and so on.
2) That's a single point of failure. Think about using SoFS instead of a single SMB3 share and think about clustering your target (you'll need a separate fault tolerant back end of that) to increase uptime. See:
MSFT iSCSI Target Failover Cluster
http://techontip.wordpress.com/2011/05/03/microsoft-iscsi-target-cluster-building-walkthrough/
Good luck! :)
StarWind VSAN [Virtual SAN] clusters Hyper-V without SAS, Fibre Channel, SMB 3.0 or iSCSI, uses Ethernet to mirror internally mounted SATA disks between hosts.