As you know, Win98's VCache disk cache is important for improving hard disk performance. This is because the disk cache caches or stores data from the hard disk in the much faster RAM so that if a program requires that piece of data, it can just access the disk cache for it, instead of loading from the hard disk. The disk cache can also read ahead by copying more data than what the program asked for in the assumption that the following consecutive data segment will be needed next. These are some of the methods employed by the disk cache to improve your hard disk's performance. More information on optimizing the disk cache can be found in the Disk Cache Optimization article.

But what exactly is chunksize and what has it got to do with the disk cache? Well, to organize the data stored in the cache, the RAM used for the cache is divided into smaller units, just like hard disk space. Each of these units or chunks of cache are now like containers in which Win98 can store cached data. The size of each chunk is the chunksize of the disk cache. Like the dimensions of a container, it limits the amount of data that each chunk can store. So, the smaller the chunksize, the less data can be stored in each but there will be consequently more chunks per MB of cache. But what's the significance of this fact?

How Can Chunksize Affect The Disk Cache?

If the chunksize is set to a small value, each chunk as noted above will be able to store less data but there will be many more chunks per MB of the disk cache. The disk cache can then make more efficient use of each chunk. Instead of flushing data from a single large chunk of cache just to store a small dataset, the disk cache can now flush a few small chunks that is just large enough to cache that dataset. In short, there will be less wasted cache space. However, due to the larger number of chunks being managed, there will be a larger overhead for all cache transactions.

On the other hand, the chunksize can be increased so that there will be fewer chunks (for a given cache size) to manage. This will lower the overhead of the cache but because there are fewer chunks per MB of cache, the disk cache will have to store data in larger and less efficient chunks.