Java Glossary : martha

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martha

A program that dynamically keeps the most active files in the prime real estate near the outer edge (near the beginning of the disk) near the swap file and the directory, and the least active files, and the bulk of the disk space in the inner tracks (near the end of the disk). This could be done on per cylinder basis, or per file or per cluster. A martha might live inside a hard disk's firmware, and operate totally transparently to the operating system, completely unaware of the operating system's file and directory structure, working at the raw cluster level. The disk drive itself keeps a map of logical to physical disk addresses. It does all new writes in prime real estate, and, in the background when it has nothing better to do, copies material not accessed for a while from prime real estate to the not so prime real estate to free up prime space. Data in prime space freed up this way is tracked in both prime and not so prime location. Reads are are done from the closest copy. The prime copy will likely be soon overwritten. The martha attempts to keep the data physically sorted in order by likely next access, and likes to keep a pool of instantly freeable (but possibly occupied) space in the prime real estate. It constantly adjusts its logical to physical map so that the computer is totally unaware it is doing this. The computer just sees extraordinarily fast seeks. Write seeks are all fast. Read seeks are fastest to files or parts of the disk that have been accessed most recently. However, unlike a cache, the speedup effect falls off gently with time. The etymology of the term martha honours Martha Stewart, a woman known for her boundless industry and astounding powers of tidiness and organisation.

To write an efficient disk defragger, model how you tidy your apartment, better still, how Martha Stewart tidies her house.

disk defragger student project that also touches on marthas

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