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Storing mosaic datasets

Mosaic datasets—the data model for managing raster data in ArcGIS—can be stored in a file or enterprise geodatabase. In most cases, file geodatabases are used, as they provide fast access and required scalability for most applications. The main application for using enterprise geodatabases is in workflows where multiple users may be editing the mosaic dataset simultaneously, as well as scaling to large enterprise or cloud implementations. These workflows will generally assume file geodatabases are being used, but the process of using enterprise geodatabases is the same.

Location of mosaic datasets

When working on small collections of files connected via a removable drive, many users store the mosaic dataset in a root directory of the data. The advantage of this is that should the drive letter or location of the files change, ArcGIS will still be able to access the imagery, as the system will look for files in a relative path to the mosaic dataset if the imagery cannot directly be accessed. For larger implementations and optimization, as a general rule, it is better to store the mosaic datasets in a separate set of directories dedicated for mosaic datasets, making it simpler to optimize access to these small files and assist in backing up. By default, when overviews are created for mosaic datasets, they are stored in the same location as the mosaic datasets. In cases where these overviews are small, this is suitable, but when working with mosaic datasets that have large overviews, it is often advantageous to define the location of the overviews when the overviews are created so that they are stored similarly to the imagery.

File geodatabases provide very good performance, but access by desktop or server can be very chatty, with large numbers of requests made to the file system. It is therefore advisable to store the mosaic datasets on a drive to which the server has fast access. Often it is better to ensure that the file geodatabase is on a faster direct-access drive on the server. This is especially true when working with mosaic datasets that contain hundreds of thousands of records. If a large mosaic dataset is stored in a network file share, this can be detrimental to performance. One popular pattern is to store the mosaic dataset being used for authoring on a NAS or SAN, then prior to publishing, copy it to the appropriate servers using a directory name that is the same as the original.

Naming of mosaic datasets

When using large numbers of different mosaic datasets, it is often useful to adhere to a standardized naming convention. These documented workflows will use the following prefixes:

S_xxx-Source mosaic dataset

D_xxx-Derived mosaic dataset

R_xxx-Referenced mosaic dataset

Number of mosaic datasets per geodatabase

A single geodatabase may contain a large number of different mosaic datasets. For file geodatabases, there is no significant advantage to storing multiple mosaic datasets in a single geodatabase. Typically, either a separate geodatabase is used for each mosaic dataset or a small group of related mosaic datasets that define a project are stored in a single geodatabase, making backup and restoring simpler.