Difference between SIZE and SIZE ON DISK on a pc? Why is SIZE ON DISK always greater?



When looking at the properties of a file on a PC, there are two numbers that stand out: size and size on disk. While both of these are related to the size of the file, they can often be very different. In this article, we will explore the difference between the two and why size on disk is often greater than size.

Size is the amount of data contained within a file. This is the original size of the file, before any modifications or alterations are made. It is calculated by counting the number of bytes that make up the file. For example, if the file contains 1,000 bytes, its size would be 1,000 bytes.

Size on disk, on the other hand, is the amount of disk space a file occupies on the disk. It is always greater than size because of the way files are stored on a hard drive. Every file is stored in a cluster of sectors on a disk, and when a file is created, the cluster must be prepared for the file size. This means that the size on disk will always be greater than the file size, as the cluster must be large enough to accommodate the file.

The amount of space required for a file depends on the file system. For example, FAT32 requires more space than NTFS, as it stores more information in the file system. Also, if the file is compressed it can take up less space on the disk than its uncompressed size. Compression algorithms can reduce the size of a file considerably, making it fit in a smaller space on the disk.

In conclusion, size and size on disk are two different measurements related to file size. Size is the amount of data contained within a file, while size on disk is the amount of disk space a file occupies. Size on disk is always greater than size due to the way files are stored on a hard drive, as well as the file system and the compression algorithms used. Understanding the difference between the two can help IT admins better manage their storage and ensure files are stored efficiently.

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