Recently needed to extract a small "chunk" from a collection of adjacent MrSid mosaics, each about 4Gb in size. Once again, GDAL came to the rescue, and saved much time and agony wile working with very large, compressed, and proprietary-format files. Two lessons learned:
The GDAL VRT format can save a lot of time and effort by providing access to a collection of files without actually altering the originals.
ArcGIS 9.x does not like BigTIFF files. When file sizes approach or exceed 4Gb, the HFA format is a nice alternative.
Have patience, subsetting a chunk out of 5 adjacent MrSid files (4Gb each) took about 7 hours. Fun experiment: extract sub-chunks from each of the constituent sid files and distribute across CPU cores.........