The best allocation unit size for music.

[bluesman]

50 minutes ago, AudioDoctor said:

The what now?

Allocation (or cluster) size is the minimum amount of storage space any file can occupy on a drive.  Even if you add a text file with one word in it, that file will occupy one allocation unit on the drive and the unused part will remain empty.  If you add a 5k file to a disk with a 4096 allocation size (a common default), that file will occupy two allocation units (wasting the empty space).

 

Operating systems have default allocation unit sizes that are almost always the best and most practical choice. I've played with multiple settings and can't identify any performance difference at all on multiple computers and operating systems for music (or for any other normal use).  So I just use the default setting when formatting.

 

Just for information, a very small allocation size contributes to disk fragmentation (scattering of pieces of a single file across entire drives).  This could be a big problem for older, smaller HDDs but is no longer a performance issue for most drives and users.  Most OSs have a defragmentation function built in.  There's also a lot of open source and proprietary defragging software out there - but you probably don't need it.  Do not defrag SSDs - they absolutely don't need it.....ever.  In Win10, open "Defragment & Optimize Drives" by entering defrag into the Settings search pane.  You'll get this window:

[bluesman]

2 hours ago, AudioDoctor said:

@bluesman thanks for the comprehensive answer.

 

I'm not on Win of any sort, or even Mac OS so I'll just have to suffer through not knowing. I did know not to attempt to defragment an SSD. Not that I have had to even think about defragmenting a drive in probably a decade or more anyway. I know my Linux install has a trim setting that works weekly, and that's all that's needed.

It’s the file system that asks you to set allocation size when you format a drive.  Modern Linux uses ext4, and the default is also 4K.  You can run into mounting problems when block size is bigger than page size, and there’s no performance advantage to going above the default.  So stick to the default and you’ll be fine.

[bluesman]

1 hour ago, sphinxsix said:

AFAIK it does matter as far as balance between the wasted disc space vs read speed is regarded, eg often people who like to stream (or record) a couple of movies at the same time use quite big AUSs on their HDs

I’ve run benchmarks on current HDs (WD Red and Seagate Iron Wolf) using tiny and huge clusters, and the difference in random read and write performance is negligible.  Others have found the same thing. This project was done 8 years ago, so the discs tested were not as fast as the new ones I used a few months ago when I got my new Asustor NAS - but the results are the same as mine:

“The speed differences seen in this test between the large sizes and the default size were not significant enough to recommend large sizes...I was curious to see whether there are obvious benefits to large cluster sizes.  Apparently, there are not.”

Poorly chosen cluster size can interfere with function, eg NTFS cannot compress files with clusters bigger 4k. It can also affect RAID, since stripe size is independent of allocation and should always be equal to or bigger than cluster size. If bigger, stripe size should be in multiples of cluster size for best performance and efficiency.  There’s little (if any) reason to use other than the default allocation for a given file system.