Handles all synchronization of metadata for file

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handles all synchronization of metadata for file system I/O on the shared LUN and is the only node where NTFS is mounted. An example of such metadata would be the file system changes that occur when a virtual machine running on a Hyper-V cluster is turned off. Such metadata changes are routed over the SMB path to the coordinator node. By contrast, file system I/O that is not metadata is sent directly down the stack to the storage to provide direct I/O performance. In Windows Server 2012, the Failover Clustering feature handles orchestration of file system changes on CSV disks by performing orchestration separately for each LUN. This meant that if you had eight cluster nodes using four LUNs for shared storage, you had to manually spread the CSV disks across the cluster. Also, Failover Clustering in Windows Server 2012 had no built-in mechanism for ensuring that they stayed spread out. In fact, all of the CSV disks could be owned by a single node. Failover Clustering in Windows Server 2012 R2, however, now includes a mechanism for fairly distributing the ownership of CSV disks across all cluster nodes based on the number of CSV disks each node owns. Rebalancing ownership of CSV disks happens automatically whenever a new node is added to the cluster, a node is restarted, or a failover occurs. Another enhancement in Windows Server 2012 R2 is when a workload, such as a virtual machine running on a Hyper-V host, attempts to establish an SMB 3.0 connection with a SoFS, the SoFS will try to determine whether the workload has an optimized I/O path it can use to access the CSV disk using direct I/O. One of the key improvements with Failover Clustering in Windows Server 2012 was that CSV disks could perform more operations in direct I/O mode than occurred in Windows Server 2008 R2. Direct I/O can be used with storage that has Fibre Channel, iSCSI, or SAS connectivity and involves writing directly to a CSV disk. Drivers for devices that can transfer large amounts of data at a time can use direct I/O for those transfers, and using direct I/O for such transfers improves a driver’s performance, both by reducing its interrupt overhead and by eliminating the memory allocation and copying operations inherent in buffered I/O. Increased CSV resiliency CSV in Windows Server 2012 R2 now has health monitoring of the Server service to help increase the resilience of your Failover Clustering solution. This is important because if the Server service becomes unhealthy on a failover cluster, it can impact the ability of the CSV coordinator node to orchestrate metadata updates and accept I/O requests from other nodes. To protect against this, when the Server service is detected as being unhealthy in a Windows Server 2012 R2 failover cluster, ownership of the CSV is automatically transitioned to another node in the cluster.
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CSV and other storage features CHAPTER 4 73 Another improvement is that multiple Server service instances are now allowed per failover cluster node. Specifically, you can now have:
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