Across the computing spectrum, there are many different formats of secondary storage and file management all based on the same building blocks. While they come by different names, NTFS, HFS+, and ZFS, the file system management systems of Windows, Mac OS and Solaris Unix all have several characteristics that assist them in managing your data.
In all file management systems, there has to be a consensus first on how big (or small) a single increment of data will be. This increment, known as a block, size is the smallest space the system will address. This is a variable set at the time of the creation of the Volume format. Choosing a smaller block size will result in less wasted space in the file system but a loss in performance due to management of more blocks. Conversely, choosing a larger block size results in fewer blocks and increased performance with less management, but results in more wasted space within the file system. Block sizes for the mentioned systems range from 512bytes to 4k.
These three file management systems have many parameters that govern attributes of the files created in them. These parameters include, but are not limited to, file size, file name size (characters), character sets that can be used to name files, such as ASCII, unicode or UTF-16. Character sets can be case sensitive or insensitive depending on the System. In all three to the mentioned file systems above, case sensitivity is an optional characteristic. Why is letter case important? As you build directories, new files within a directory cannot have the same name as an existing file in a directory. Having a file system that is case sensitive and preserves the case of the characters allows for more naming options.
The Apple default for HFS+ file system us a block size of 4k (4096bytes). As each block on the hard drive can hold no more than this about of data, was files are written, the information is written to, when possible, consecutive sectors or blocks on the disk. When does this size become a problem? As this is the minimum block size, files less than 4k will be contained within a single block and the remaining area of the block will be left empty. If the system is to write many files smaller than the single block, there will be an accumulation of empty space on the disk that cannot be written to.
So what are the pro and cons of block size? With a smaller block size, you are less likely to have ‘holes’ on the disk of unused space. You will also lose some performance of the unit as more time is spent managing the larger number of total blocks. With larger block sizes you have bigger ‘holes’ but the is less time spent managing the blocks and content of the disk.