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Administration best practices
26 Dell EMC SC Series: Microsoft Windows Server Best Practices | 680-042-007
3.13 Offloaded Data Transfer
Offloaded Data Transfer (ODX) is a feature developed by Microsoft that offloads data copy and move
operations from Windows hosts and network switches directly to the storage array. Offloading data copy and
move operations to the SAN reduces the demand for CPU and bandwidth resources on the host servers,
NICs, and networks switches. In addition, overall copy and move performance for data can be significantly
faster with ODX.
ODX is enabled by default on Windows Server 2016 newer and is supported with SCOS 6.3 and newer. ODX
should normally be left enabled, except when there is a need to obtain ODX instead of non-ODX performance
benchmarks or to perform troubleshooting.
ODX requires the source and destination volumes be formatted as NTFS volumes, and be located on the
same SC Series array. When volumes from different SC Series arrays are mapped to a host server, data
transfers between these volumes will use standard network copy instead of ODX.
ODX operations can be initiated from a physical server or a virtual machine. The source and destination
volumes can be physical disks, VHDs, or SMB shared disks (the share must be hosted on a volume located
on the same SC Series array as the source/destination volume).
Within Hyper-V, ODX is used to speed up the virtualization platform layer. This allows Hyper-V to achieve
native-like performance when virtual machines read and write to the SC Series array. ODX also allows for
rapid deployment of guests.
Additionally, ODX can be utilized when creating a fixed-size virtual hard drive (VHD). Without ODX enabled,
Windows will explicitly zero-out all the disk space assigned to the new VHD file. Depending on the size of the
VHD file, this can be a slow, time-consuming process. With ODX enabled, Windows issues the SC Series
array a command to write all zeros to the blocks that represent the new VHD file. This process takes seconds
to complete. Windows reads the newly created VHD file as the full size, but with thin provisioning on the SC
Series array, the file is not consuming any actual space until data is written to it.
ODX operations on VMs require the VMs be running Windows Server 2012 or above, or Windows 8 or above,
and the VM virtual hard drive(s) must be in the VHDX format. Transferring data between VMs requires that
the virtual hard drives of both VMs be housed on volumes hosted on the same SC Series array. VMs can use
ODX to transfer data to other guests, physical pass-through volumes, virtual Fibre Channel volumes, and
SMB shared disks.
For information on how to enable or disable ODX, and how to establish performance benchmarks, see the
Microsoft Windows IT Pro Center.
3.14 Resilient file system
Introduced with the initial release of Windows Server 2012, Resilient file system (ReFS) is a file system that is
specifically intended for managing extremely large data volumes. Using a new file system design, ReFS can
auto-detect data corruption and automatically perform needed repairs without taking a volume offline. ReFS
eliminates the need to run chkdsk against large volumes.