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Standard 2: XAM|
XAM is the other major storage management standard being developed by SNIA. XAM will make fixed content (data that doesn't change once it's created) easier to manage. It does this by freeing the data from dependencies on location, apps and storage devices. XAM attaches a unique identifier and user-defined meta data to each data object to make it faster to find. It virtualizes the interface between the storage devices and the apps to minimize the pain in changing hardware or software.
XAM meta data can range from standard information like date of file creation or file size, to more elaborate and project-specific information such as which project the data is associated with. The user (or system) can specify that some of the fields can't be changed while others can be modified.
By storing the meta data in separate fields and welding it to the data to create a single object, XAM makes it a lot easier to find, track and manipulate data. By making those fields fixed or modifiable, XAM protects the audit trail (which needs fixed fields) and updates other parts of the meta data as needed. New fields can be added as business requirements change.
In XAM, as in other content-based storage, every data item and its associated meta data has a unique identifier. "XAM supports unique IDs for the data," says David Martin, co-chair of SNIA's XAM committee and an information
| portfolio manager at HP. "No matter where the object gets transferred, that identifier is always going to be the identifier for that object. We can find that needle in the haystack, no matter what haystack the needle has been moved to."
XAM virtualizes the interface between app and hardware. That means apps can access hardware through a standard interface for any device that supports XAM, says Martin. That makes management easier, and removes much of the worry of migrating to new hardware.
The XAM architecture is based on the XAM Library, which implements the XAM API and sits between storage devices and the app. The XAM Library is part of the XAM Software Development Kit (SDK), which dynamically links apps that want to use the XAM system to the storage devices. The library contains Vendor Implementation Modules (VIMs), vendor-written code that translates XAM requests into device-specific action. One of the beauties of XAM is that vendors don't have to change their products to use it. Instead, vendors write VIMs for the library and XAM handles the rest.
This was first published in January 2008