To publish mosaic dataset: better in SDE or in File GDB?

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03-25-2014 07:23 AM
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Occasional Contributor
I am to publish a mosaic dataset via ArcGIS Server with the Image extension.

Which of ArcSDE or file geodatabase is the more efficient at hosting a mosaic dataset to be served through AGS? I think I've seen a post somewhere proclaiming the advantage of the file GDB for this purpose, and I believe it's mostly due to it keeping the overview rasters out of ArcSDE. Perhaps there's a performance advantage to the file GDB, and other reasons as well, but I'm uncertain. Isn't ArcSDE quite fast at serving rasters, particularly with the AGS Image extension? I'm really puzzled.

Please be aware the ArcSDE geodatabase that hosts the vector data runs on a SQL Server instance shared with a few other departments.

So I'd like some opinions, please, on which database is more likely to serve the imagery faster and why.

Thanks in advance,
Justin
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Esri Esteemed Contributor
The ability to populate rasters in a database was great when it was introduced with ArcSDE 8.0,
but that ship has sailed (and foundered on rocks and sank).  Disk-based imagery access is where
you want to be now. 

- V

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Esri Esteemed Contributor
The rasters aren't coming out of ArcSDE, just the path to the file on disk.

It will *ALWAYS* take longer to get data out of an RDBMS than a file geodatabase,
just because the RDBMS needs to enforce ACID.  But the difference is likely to
be on the order of milliseconds, so you'd wouldn't notice it without a programmatic
timer (which is likely to consume milliseconds in operation).

The principal difference between an enterprise geodatabase and a file geodatabase
would be if you had a cluster of ArcGIS Server hosts, where remote database access
might have an edge over remote file access.

- V
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Thanks for the reply, Vince. That's very helpful, but let me explain what I meant by "keeping the overview rasters out of ArcSDE."

In my initial post I did not mention there is an existing reference mosaic dataset in the SDE gdb that I'm referring to in this thread. Last week I ran Export Raster Catalog Paths on it (because Export Mosaic Dataset Paths does not work for a referenced mosaic), and in the output found paths that do indeed point to TIF files on disk, as would be expected. I did also, however, find dozens of paths similar to the following two:

\\winston\GISImagery\SWOOP2010\orthos\overviews\viewer1@bc@winston.sde\bc.GIS_ADMIN.AMD_SWOOP2010_OVR\\Ov_i05_L01_R00000972_C0000038C

and

C:\Users\kraemerj\AppData\Roaming\ESRI\Desktop10.1\ArcCatalog\sde@bc@winston.sde\bc.GIS_ADMIN.AMD_SWOOP2010_CAT\Raster.OBJECTID=18853

By the way, I don't know why the sde@bc@winston connection appears in some paths because I never create feature classes as the sde user. This mosaic had been loaded from a raster catalog, so perhaps it had something to do with no coffee the morning I created that catalog 😉

The overviews folder on disk (named in the first path above) contains nothing but two .sde connection files, so from these facts it appears the overviews are indeed stored in the SDE gdb. I've just checked the tool help for Build Overviews, and found:

"The overviews generated for mosaic datasets on the SDE are stored within the geodatabase containing the mosaic dataset. These locations can be changed by first using the Define Overviews tool and specifying a location."

So based on the fact I could use Define Overviews to specify the output location for overviews to produce them on disk, regardless of whether SDE or fgdb is host for the mosaic, and that mosaic performance hosted in SDE vs. fgdb will be just minimally different, my question becomes "is it better for image service performance to generate mosaic overviews on disk, or allow them to be created in SDE?
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Esri Esteemed Contributor
The ability to populate rasters in a database was great when it was introduced with ArcSDE 8.0,
but that ship has sailed (and foundered on rocks and sank).  Disk-based imagery access is where
you want to be now. 

- V

View solution in original post

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Highlighted
Occasional Contributor
The ability to populate rasters in a database was great when it was introduced with ArcSDE 8.0,
but that ship has sailed (and foundered on rocks and sank).  Disk-based imagery access is where
you want to be now. 

- V


I know now what to do. Thank you very much, Vince.
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