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Multiple transports and volume mapping
39 Dell EMC SC Series: Microsoft Multipath I/O Best Practices | CML1004
9 Multiple transports and volume mapping
On an SC Series array that is configured to use multiple front-end transports concurrently, mapping volumes
to host servers using multiple transports is supported, however, there is limited Windows Server support.
For example, if the SC Series array and a host server both support FC and iSCSI, when mapping a new
volume to the host, all available FC and iSCSI paths will be mapped by default.
9.1 Limited Windows Server support
Using mixed transports concurrently on the same Windows volume has limited Microsoft support and should
generally be avoided, unless there is a good reason (usually, temporary) to do so.
With Windows Server 2012 R2 and newer, when an SC Series volume is mapped to a host server using
multiple transports (for example, FC and iSCSI concurrently) Windows Server will use an algorithm to
arbitrarily choose a preferred transport (typically Fibre Channel wins) and the host will ignore the other
transport. The problem with this default Windows behavior is the risk of service interruption. If all paths for the
preferred transport go down, the host will not start using the alternate transport without a manual disk re-scan
or server reboot.
9.2 Use cases for multiple transports
A common reason for using multiple front-end transports at the same time is when an environment is in the
process of migrating from one transport to another.
Regardless of the use case, the best practice is to only use a single transport for any given volume. A host
could have one volume mapped using FC, and another volume mapped with iSCSI. Windows treats each
volume independently from the standpoint of the transport used.
9.3 Configure a volume to use a single transport
When multiple transports are available, limit volume mappings to a single transport by following these steps:
1. Log in to the Dell Storage Manager client.
2. On the SC Series array under the Storage tab, expand Volumes and locate the desired volume.
3. Right-click the volume and select Map Volume to Server. The Map Volume to Server window
appears.
4. Select a server to map the volume to and click Next.
5. Click Advanced Options.
6. Under Restrict Mapping Paths, uncheck the box to Map to All Available Server Ports.
7. Select one of the following:
a. Map using specific server ports (check the specific server ports desired).
b. Limit ports by transport type (available only if the SC Series array is configured for multiple
transports; select the desired transport from the drop-down menu).