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12 Dell EMC SC Series: Microsoft Windows Server Best Practices | 680-042-007
are collocated that have different transport requirements. It is also common during a transition period if an
environment is migrated from one transport to another.
SC Series storage supports mixed transports
Configuring any given volume (mapped to a host server as a LUN) to use multiple transports generally should
be avoided because it increases design complexity unnecessarily and can introduce unpredictable service-
affecting I/O behavior in path failure scenarios.
For example, a Windows Server (2012 R2 and newer) OS will detect the presence of FC and iSCSI paths
when a LUN with multiple transports is mapped to it, but during discovery, the host will choose a primary
transport based on an enumeration algorithm which typically results in the host selecting the Fibre Channel
paths to pass I/O and will ignore the iSCSI paths. The problem is, if all paths for the primary transport go
down, the host server will not automatically start sending I/O using the alternate transport without a manual
disk re-scan or host reboot which can obviously be service-impacting.
Because there is limited Microsoft support for using mixed transports for any given LUN, it not recommended
as a best practice. In addition, in a cluster environment, all nodes should be configured to use a uniform
transport (FC, iSCSI, or SAS).
There are some use cases where using mixed transports on the same Windows host may be necessary, such
as when migrating the overall environment from one type of transport to another, and both transports need to
be available to a host during a transition period. If multiple transports must be used, use a single transport for
any given LUN.
• Map a LUN to a Host using FC paths only: Acceptable
• Map another LUN to the same Host using iSCSI paths only: Acceptable
• Map a LUN to a Host using FC and iSCSI paths concurrently: Not recommended