In any storage system, the one feature that is of paramount importance to the user is data protection. While the user takes for granted that data will not be lost due to a system crash or a design bug, the user also expects a storage system to protect him from inadvertent deletions, unwanted modifications, malicious agents and the like.

In response to this most basic need, snapshots have become an industry-wide standard for protecting data at a very fine granularity. Whether commissioned according to a schedule or under the direction of an administrator, the data snapshots taken by a storage system represent point-in-time pictures of the contents of a volume in a storage system, similar to an incremental backup of the system’s data. What distinguishes snapshot implementations from vendor to vendor is the manner in which the stored data is backed up, as this can greatly impact both space utilization and performance. The StorTrends® line of storage appliances from American Megatrends, which utilize the innovative StorTrends® iTX storage software, offer industry-leading support for snapshots, with an implementation that optimizes performance and storage capacity utilization.

While snapshots present a consistent state of the volume to the user in terms of the outstanding I/Os to the storage server, this state may not be consistent with respect to the application using the volume, particularly in terms of its recoverability. Moreover, it is often the case that an application is using multiple volumes on the storage server for various purposes. For example, Microsoft Exchange Server uses both a log volume and a data volume to maintain, manage and protect its data. Thus, a snapshot of both volumes must be synchronized in order to achieve application recoverability, since these two volumes can not function independently of each other. Also, often the I/Os are being cached on the initiator, which can be doing delayed-writes to the volume, meaning that the snapshot taken from within the storage server does not always assure application-consistent data recoverability during a disaster.