What is cluster size and which is the best one to use?
Basically, cluster size is the allocation of space on your hardrive. 1 file will use at least 1 cluster and no 2 files can use the same cluster. If your cluster size is 1k for example, a 32k file will use 32 clusters. If your cluster size is 32k, that same 32k file will use 1 cluster. Usually, using the default cluster size will suffice for most users and it is determined by the volume size. Sometimes it can be an advantage to use a custom cluster size.
Extreme examples would be where you would use small cluster sizes if you have alot of small files and you want to maximise the storage space on your hardrive, this tends to slow down the file system, but optimises the storage due to less waste for each cluster. The other extreme could be where you work with mostly large files, ( a volume for video capture ) you may want large cluster size because you aren't concerned with wasting space, and larger clusters tend to speed up the file system and can help eliminate dropped frames. Most users will lie somewhere in the middle of these extremes, using both large and small files, and the default will work fine.