. SLACK FILE SLACK RAM SLACK DRIVE SLACK DISK SLACK CLUSTER SLACK SPACE LIMITATION SLACK SPACE REDUCTION
SLACK ● Slack is the space wasted due to unused storage at the end of the last cluster used to store the data in each file. ● When a great number of files are stored on a disk with a large cluster size, a lot of the disk is wasted due to this overhead. ●There are two types of slacks:- ●FILE Slack. ●RAM Slack.
FILE SLACK Files are created in varying lengths depending on their contents. DOS, Windows and Windows NT- based computers store files in fixed length blocks of data called clusters. The data storage space that exists from the end of the file to the end of the last cluster assigned to the file is called "file slack".
. File slack potentially contains randomly selected bytes of data from computer memory. This happens because DOS/Windows normally writes in 512 byte blocks called sectors. Clusters are made up of blocks of sectors.
RAM SLACK If there is not enough data in the file to fill the last sector in a file, DOS/Windows makes up the difference by padding the remaining space with data from the memory buffers of the operating system. This randomly selected data from memory is called RAM Slack because it comes from the memory of the computer.
DRIVE SLACK RAM slack affects only to the last sector of a file. If additional sectors are needed to round out the block size for the last cluster assigned to the file, then a different type of slack is created. This slack is called as drive slack and it is stored in the remaining sectors which might be needed by the operating system to derive the size needed to create the last cluster assigned to the file.
EXAMPLE Let's say that a file is created by writing the word "Hello" to a file. Assuming that this is the only data written in the file and assuming a two sector cluster size for the file, the data stored to disk and written in file slack could be represented as follows: Hello+++++++++++++++++++|-----------------------(EOC) RAM Slack is indicated by "+“ DRIVE Slack is indicated by "-"
DISK SLACK Space allocated to a disk file but not actually used to store useful information. Those unused storage space in disk is known as disk slack.
CLUSTER The storage of data in fixed length blocks of bytes called clusters. Clusters are essentially groupings of sectors which are used to allocate the data storage area in all Microsoft operating systems.
SLACK SPACE The DOS and Windows file systems use fixed-size clusters. Even if the actual data being stored requires less storage than the cluster size, an entire cluster is reserved for the file. The unused space is called the slack space. DOS and older Windows systems use a 16-bit file allocation table (FAT), which results in very large cluster sizes for large partitions.
LIMITATION WASTAGE OF MEMORY SPACE FOR EXAMPLE : If a file is 1K in size and the cluster size is 32K, then 31K of “slack” space is wasted for that file.
SLACK SPACE REDUCTION The obvious way to reduce slack space is to decrease the block size on your hard disk. This is theoretically possible in two ways:- Increase the maximum number of directory entries. Decrease the size of your disk.
1. Increase the maximum number of directory entries The number of directory entries is determined by the operating system and is therefore not easy to alter. 2. Decrease the size of the disk. The capacity of your hard disk is also fixed, however, it is possible to redistribute the capacity of your hard disk. It is possible to do this by partitioning the hard disk.
PARTITIONING To divide memory into isolated section. There are two types of partitioning: - Hard partitioning. Hard partitioning is the same as DOS partitioning -- the disk is physically divided into different sections. Soft partitioning. Soft partitioning, on the other hand, does not physically affect the disk at all.
CONCLUSION File Slack is created at the time a file is saved to disk. When a file is deleted under DOS, Windows, Windows 95, Windows 98 and Windows NT/2000/XP, the data associated with RAM slack and drive slack remains in the cluster that was previously assigned to the end of the 'deleted' file. The clusters which made up the 'deleted' file are released by the operating system and they remain on the disk in the form of unallocated storage space until the space is overwritten with data from a new file.