Swap File Speed Vs. Partition
Multitasking computers use random access memory, or RAM, to store program data during execution. To facilitate the growth of complexity and resource requirements in computers, particularly when RAM on a computer came at a premium, developers created the concept of "swap" space to help mitigate the demands on the RAM of a system. Linux systems, in particular, take advantage of swap space, either in the form of a swap partition on the hard drive or a swap file. Each of these options come with differences in speed of access.
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Swap Space
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Computer operating systems use swap space to manage memory usage. Swap space maps the memory located in RAM to a separate area on the hard drive, known as "virtual memory." This permits the kernel of the operating system to allocate memory to applications that might not exist in the actual RAM space. For example, the operating system might allocate more memory than is readily available for a program by "swapping" data pages in memory that are not in use.
Partitions Versus Files
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Swap partitions represent the most common form of swap space. In this method, the partitioning software designates a partition of the hard disk as swap space. Swap files, on the other hand, do not use a separate partition of hard disk space, but exist in a file on the main hard disk, usually as part of the root partition of the OS installation. Swap files are special files that behave in the same way as a swap partition, by allowing the OS to write data pages from memory to the file and use the space for other applications.
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Speed and Access Differences
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In theory -- and this has been the case in early computing -- a swap partition will operate much faster than a swap file. Since the partition is a dedicated swap space, complete with contiguous memory, the operating system can set up a specific swap file system on that partition to aid in page data swapping. Swap files, on the other hand, are just another file in the main disk system, and like other files, is prone to fragmentation. This means that the swap file's data exists in multiple locations on the hard drive. The hard drive must put in extra effort to read blocks of memory from various locations on the disk, which slows access time.
Mitigating Speed Differences and Uses
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Generally, while swap partitions offer faster access to data, most modern operating systems manage both swap files and swap partitions in such a way as to make the speed difference negligible. The Windows operating system relies by default on a swap file, and has built-in optimization controls, as well as user-modifiable options to make using the swap file quick and painless. In Linux, the introduction of the 2.6 kernel has also minimized this difference, and the tradition of creating swap partitions becomes a question of organization, rather than speed.
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