There are two methods of loading data from QVDs: optimized and non-optimized. The key point here is that the optimized loads can be up to 100 times quicker than the non-optimized loads.
This speed increase is a result of the data passing directly from the disk (QVD) into the memory (RAM) without being unpacked from its compressed QVD format.
As you may have guessed, the reason every load is not optimized is that we often want to change the data coming out of the QVD. This requires it to be uncompressed before going into memory; hence, it is significantly slower. Just about any change to the data will cause the load to be non-optimized; however, there are a few things that we can do.
