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Optimize Hyper-V for SC Series
23 Dell EMC SC Series: Microsoft Hyper-V Best Practices | CML1009
Map storage to a cluster object to ensure consistent LUN numbers on all nodes
2.11 SC Series LUN limits for larger Hyper-V clusters
For large Hyper-V clusters with many nodes, there are two LUN limits to be aware of:
The functional LUN limit: Although the SC Series storage supports up to 254 LUNs per cluster server
object, resources on Hyper-V server nodes might be consumed before the physical limit of 254 LUNs
reached. This will vary depending on the capacity of the hardware and the workload.
The physical LUN limit: Depending on the Hyper-V cluster design (for example, if using pass-through disks),
it is possible to consume many LUN numbers quickly, exhausting the pool of free LUN numbers.
It is also important to note that a small number of available free LUN numbers must be kept in reserve for an
administrator to use for scratch volumes, temporary volumes, or SAN maintenance. SAN maintenance might
include operations such as expiring snapshots or SC Series Replay Manager restore operations that require
LUN numbers on a temporary basis when presenting View Volumes from snapshots to a host using in-guest
iSCSI.
To avoid reaching the LUN number functional or physical limit for a Hyper-V cluster, consider some of the
following strategies:
• Many-to-1: Use a many VMs-per-CSV strategy when using virtual hard disks.
• Direct-attached: Use direct-attached storage (iSCSI or virtual Fibre Channel) to present SAN
volumes directly to guest VMs instead of pass-through disks, if using direct attached/pass-through is
required.
• Increase number of data paths: Add physical FC or iSCSI cards to the cluster nodes to expand the
functional limit. This will not increase the 254 LUNs-per-SC Series cluster server limit.
• Smaller cluster size: If using pass-through disks, create smaller Hyper-V clusters with fewer nodes
and fewer guest VMs instead of larger clusters with more guest VMs.