Owlcom software
basadO wlCom  Software
Let's Owl manage your files
Welcome Screenshots Buy now Download Write to Owl Subscribe to news FAQ Links

Organization of the file system

the integrity of the file system. They can run after loading or after the crash and carry out a variety of scanning multiple file system data structures in search of contradictions. There are also heuristic test. For example, to find the index node number, which exceeds the number on the disk or finding files in user directories belonging roots. The Office of bad blocks. The existence of bad blocks on the disk normal. A bad blocks is usually described as disk blocks for which an amount calculated Control-readable data does not match the amount held by a control. Often appearing in the operation. Sometimes they already exist in the supply, together with the list because very difficult for suppliers to make disk completely free of defects. Two solution to the problem of bad blocks, one at a different level sensor OS kernel level. The first way is to keep the list of bad blocks in the disk controller. When the controller is initialized, it reads bad blocks and replace the defective unit standby, marking the display of the list of bad blocks. All real requests will be to go to the contingency block. It should be noted that this mechanism lift (the most common mechanism for processing requests to the disk block) will be working inefficiently. The fact is that there is a strategy of priority requests to the disk (see Chapter O). The strategy dictates the direction of the head disk reader to the correct cylinder. Usually blocks placed on standby outside the cylinder. If a bad block is located at the internal cylinder, and predictive controller implements a transparent manner, the apparent movement of the ball will be done to the internal cylinder, but the actual to the outside. This is a violation of the strategy and, consequently, less the scheme. Decision-level OS might be as follows. First, it is necessary to carefully design a file containing bad blocks. Then they are removed from the list of free blocks. Then you need to make to this file has not been hits. If possible, the problem is solved. The performance file system The most typical technology to speed up work with the disk cache. Resorting to disk usually 100000 times slower than to memory. (Address to the memory of several hundred-nanosecond, and reading from the disk-block tens of milliseconds). Through information in the disk cache memory can reduce the number of disk operations, keeping part of the disk blocks, which were made before this treatment, in a special area of memory called a cache buffer (cache). This is possible because of the inherent properties of localization OS (localization properties of much discussion in the chapters dealing with the description of the work management system memory).
Next part
Welcome    Screenshots    Download    Buy now Write to Owl    Subscribe to Owl news   FAQ   Links  
Copyright 2004-2008 OwlCom Software .

OISV - Organization of Independent Software Vendors - Contributing Member Software Submit .NET - FREE and PREMIUM search engines submission and software submission and software promotion service. Owl Commander
Locations of visitors to this page

Valid HTML 4.01 Transitional