Achieve a similar level of reliability availability

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achieve a similar level of reliability, availability, manageability, and performance as that of a SAN. And since a SoFS can use Storage Spaces, another feature of Windows Server 2012 that allows you to use low-cost commodity disks to create pools of storage from which you can provision resilient volumes, the approach can often be much more cost-effective than using a SAN. That’s obviously good news for organizations whose IT budgets are constrained, which probably includes everyone nowadays. Figure 4-6 illustrates how a SoFS can redirect I/O over SMB to the optimal node. A virtual machine running on a Hyper-V host wants to access a file in a shared folder named Share2 on a two-node SoFS. The nodes of the SoFS are named File Server 1 and File Server 2. When the virtual machine attempts to connect to the share, it might connect to either Share2 on File Server 1 or to Share2 on File Server 2. Let’s say that it establishes an SMB connection to Share2 on File Server 1 as shown by the dashed line on the left. Unfortunately, this is not an optimal connection because the file it wants to access is actually located on storage attached to File Server 2. The SoFS detects this situation, however, and it automatically and seamlessly transitions the SMB connection from Share2 on File Server 1 to Share2 on File Server 2 as shown by the dashed arrow at the bottom. From this point until the end of the SMB session,
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Optimized ownership of CSV disks CHAPTER 4 71 to provide optimal I/O and throughput, the SMB connection between the virtual machine and Share2 on File Server 2 can use direct I/O as shown by the solid line. FIGURE 4-6 A SoFS can redirect I/O over SMB to the optimal node. Optimized ownership of CSV disks To ensure that a SoFS can deliver SAN-quality throughput and IOPS, Microsoft has made a couple of optimizations in how a SoFS works in Windows Server 2012 R2. We’ll begin by considering things from the perspective of CSV. Recall that CSV allow multiple nodes in a failover cluster to simultaneously have read-write access to the same LUN (disk) provisioned as an NTFS volume. This enables clustered roles to fail over quickly from one node to another node without requiring a change in drive ownership or dismounting/remounting a volume. CSV also help simplify managing a large number of LUNs in a large failover cluster. CSV work by providing a general-purpose, clustered file system layered on top of NTFS. Examples of CSV applications can include clustered virtual hard disk (VHD or VHDX) files for clustered Hyper-V virtual machines and scale-out file shares to store application data for the SoFS role.
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72 CHAPTER 4 Failover Clustering Consider a failover cluster with a bunch of nodes with a bunch CSV disks, and each CSV disk is backed by a shared LUN exposed through Storage Spaces on a SoFS. Applications running on any node have simultaneous read/write access to the shared LUN even if it is only mounted on one of the cluster nodes. The coordinator node, one of the cluster nodes,
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