Raster in FGDB vs ArcSDE: big size difference?

Question

I am exporting DEM data from ArcSDE SQL Server to File GDB (FGDB).

My FGDB's are way smaller in size.  Should I be concerned?  Why is this?  They are both Esri GRID format, correct?

For example,

Exported ArcSDE ~475GB to 320GB in FGDB.

Exported ArcSDE ~80GB to 55GB in FGDB.

Thanks!

VinceAngelo · Answer

No, ArcSDE does not use Grid (or any other file-based format) internally.  There are a number of resolutions at which to store raster values (1-,4-,8-,16-,32-bit unsigned, 8-,16-,32-bit signed, plus 32- & 64-bit IEEE float), and ways to compress tiles (both lossless and lossy).  You would need to report the actual storage bit depth, representation, compression, and tile size within ArcSDE, and the format, depth, representation, and compression in a file-based raster before any judgement could be made on concern about size change.

It's also worth noting that BLOBs expand to fill remainder of block size which can't be shared, so changing the tile size within ArcSDE could also have a significant impact on storage use within the database.

- V

jskinner · Answer

Hi Jerry,

How are you determining the size of the raster dataset in your SDE and File Geodatabases?  Are you right-clicking on the raster dataset > Properties > and looking at the 'Uncompressed Size'?

A geodatabase raster dataset will allow you to compress your raster.  You will want to compare the raster compression you have applied to the SDE Raster Dataset and the FGD Raster Dataset.