Short stroking is the process by which the capacity of a volume is reduced in order to improve drive performance. There are benefits to short stroking any mechanical disk, regardless of whether the drives are used in any type of RAID array.
The platters in a mechanical hard drive spin at a constant speed, but the sectors located at the edge of the platter are stored in approximately the same area as those near the center. As a result, these outer sectors can be read faster (MB/s) than those near the center of the platter. This can be seen in any of the hard drive benchmarking programs, where data transfer rates taper off exponentially as the head moves towards the center of the platters. HD Tune
is a popular choice for benchmarking hard drives.
By creating a small partition at the "start" (outer section) of the drive platter, you force the operating system to use only the fastest area of the drive, improving data transfer rates (for both read and write operations.)
An additional benefit of this process is that by limiting the data to a small section of the drive, the head does not need to travel as far to access data, and access times can be reduced significantly.
The effects of this can again be seen in the drive benchmarking tool, where the data transfer rates will now be more consistent across the partition, and access times will drop significantly.
(note this benchmark is on a RAID-0 pair of drives as opposed to the single drive above - meant to illustrate the more consistent drive transfer rates and subsequent higher average, and noticeable drop in access times)
There is no specific percentage of drive capacity for best result - every user should decide for themselves how much capacity is required to meet their needs. Partitions ranging from 10-25% are common, and as one would expect, slightly better results can be seen from smaller partitions.
Note: you can partition and use the remaining drive space for additional storage, but be aware that any time that storage is accessed, you will lose the performance benefits of short stroking. In practice, this works well as during most application use, the storage partition is not frequently accessed.
So, to experience the benefits of short stroking yourself, simply create a small partition next time you initialize a drive (this can also be done when building a RAID array, where you can specify the volume size) and install your operating system to this smaller partition. In almost every case, the first partition on a drive will always be located at the outer edges of the platters.
Thanks to the_beast, who has posted much of this information across multiple threads over the past few weeks. I wrote this by distilling a bunch of his posts down to a single document..