Hierarchical Storage Management (HSM) systems are being implemented in many industries to maintain and provide access to storage archives too large to keep on-line. As is well documented elsewhere, these HSM systems provide an enhanced level of security, convenience and cost savings by automatically moving (or "migrating") data to and from archival storage with no operator intervention.
In most cases, the HSM system functions like a traditional file system, retrieving or storing files as requested by users or applications. Occasionally, however, special circumstances arise where this file-by-file model is not ideal.
A good example is compound documents. A compound document might be a catalog page, where a text file is linked to one or more graphics files. In the traditional file system paradigm, the master catalog page file is requested, but the associated pictures might not be accessed until some time later, perhaps only at print time, when the system needs to send an image to the printer. This can be an inconvenience or a major problem, depending on the particular circumstance. It is an inconvenience if the user requests the catalog page file, and the text file is then retrieved from archival media, and that media is subsequently re-stored in the robotic loader. The inconvenience is felt when the graphic file is eventually requested, and the user waits seconds or minutes for those files to be retrieved. It becomes a major problem if, during a print run, the network or printer is tied up for a significant period while waiting for the graphic to be loaded.
Other examples include projects which consist of multiple files either from one or multiple applications.
In the traditional file system, each file would have to be transferred ("staged") to the on-line media manually, either at the beginning of the session or as each file was needed. Depending on the application, this can range from awkward to impossible.
The only approach to this problem in the past has been for the user to construct lists of files that would be used together, and either manually execute the staging procedure or to use a function of the HSM software to process the list of files. This rudimentary functionality can be as awkward and error-prone as the completely manual method.
A better solution was needed.
Now, LSC has created a product capability which eliminates the problem. Associative Staging in LSC's Storage and Archive Manager File System (SAM-FS) provides the solution while enhancing the effectiveness of the HSM system.
Associative Staging is an attribute that can be assigned to a file or a directory. When the attribute is enabled, accessing (and thereby staging) a file causes every file in the requested file's directory (that also has the attribute enabled) to be staged as well.
To the user the staging of the initial file proceeds in the normal manner. In the background, however, the subsequent files would also be staged, so that when the user requests them, they are immediately available. Beyond the obvious benefit of instant access to the data, this feature can also significantly reduce robot motion and media shuffling, key concerns to system administrators.
Associative Staging is a product capability developed by LSC to address the real-world storage management concerns of users. Although HSM capability has existed for a number of years, the increasing sophistication of applications and user requirements has put increasingly greater demands on storage management software. Without capabilities such as Associative Staging, many users are unable to cost-effectively implement HSM systems.
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