Windows Server 2012 brings high-availability file shares

New options for file-share availability with SMB 3 make the move more enticing, with cloudlike failover potential

Higher levels of availability have become all the rage. The days of service-level agreements (SLAs) with explicit definitions of RPO (recovery-point objectives) and RTO (recovery-time objectives) may soon be a thing of the past, as vendors promise eternal uptime for their services. It's not just cloud vendors: We now hear these promises for on-premises deployments, where there has been an increased focus on higher availability.

Windows Server 2012 has new features that make high availability easier to configure and cheaper to deploy. Where this seems to be most intriguing for admins is the new file-server-availability feature. IT admins don't typically worry about file servers or consider them sexy by any means, but what could be more mission-critical than your file servers? Everyone worries about email -- if you cannot send mail, you cannot carry on business. But if you cannot access your files, you're dead in the water, too.

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The feature is called Continuous Availability File Windows Server. It tracks file operations on highly available file shares so that clients can fail over to another node of the cluster without interruption. That definition speaks volumes in terms of what is necessary here to make this work.

For starters, behind the scenes, Windows Server 2012 offers the ability to work with SMB version 3, which allows for "transparent failover." Now you have two different file server types: classic and scale-out.

Dave Guenther, a premier field engineer at Microsoft, explains: The classic role provides this ability to fail over a file share with "zero downtime." To demonstrate the process, Guenther put together a two-node Windows Windows Server 2012 Cluster with shared storage using iSCSI and Classic File Share configured with continuous availability. The setup through the high-availability wizard was amazingly simple. Once you've configured your servers and established a file share with continuous availability, you should get complete failover from one node to another of the file share.

Another part to this classic file-server puzzle is the client. Because this is new technology, only Windows 8 supports it. If you have a Windows XP, Vista, or 7 PC involved in a large file transfer when the server goes down, the user gets an alert that the network name no longer exists. With Windows 8, there is a slight dip in transfer speed, but the file keeps trasferring until it is fully transferred. Also, volumes that use 8.3 file naming or NTFS compression do not work with it the new Windows Server 2012 transparent failover.

The other type file server -- scale-out -- is for application data (aka active-active). It lets you store application data, like Hyper-V virtual machine files, on file shares, which are online on all the nodes simultaneously. The value of these active-active file shares is that all nodes can provide file share content using SMB 3 clusters. For both Hyper-V virtual hard drives and SQL database files, using a scale-out file share on servers running Windows Server 2012 can really help ensure availability -- and you don't even need a dedicated SAN to do it.

Features like continuous availability and scale-out file servers are just two of the many new Windows Server 2012 options designed to ensure greater availability of services and data. NIC teaming, multipath I/O, support for offloaded data transfer (ODX), and single-root I/O virtualization (SR-IOV) support also sweeten the move to Windows Server 2012.

IT admins and decision makers need to take a closer look at some of these features and not write off Windows Server 2012 as just another release of the Windows Server OS. It's not. For the first time in years, I'm seeing old-hand admins getting excited again, and much of that excitement is revolving around the storage and availability features built in to Windows Server 2012.

This story, "Windows Server 2012 brings high-availability file shares," was originally published at Read more of J. Peter Bruzzese's Enterprise Windows blogand follow the latest developments in Windows at For the latest business technology news, follow on Twitter.

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