Formatting an external HDD - Which Allocation Unit Size should I use?

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dodohelp

PCHF Member
Oct 1, 2017
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Hi, I've got a 3tb HDD which I'll be formatted to fat32 using GUIFormat. I need it fat32 so my playstation and media players can read it.

GUIFormat gives me a number of options to for the Allocation Unit Size which are;
512
1024
2048
4096
8192
16384
32768
65536

The files I intend to use it for are mainly approx 700mb to 1gb (TV shows, movies etc) using it to copy across and watch. Please can somebody advise which would be the best AUS to suit my needs. I've been looking on google for about half an hour and the info on this topic is appallingly vague. Thanks
 
gus said:
https://www.techwalla.com/articles/...ld-be-used-when-making-large-fat32-partitions
Click to expand...
I was hoping that the person to reply would have advised on the question I've asked. I've already read the site you've googled. And dozens of others. Its no help. The AUS sizes they recommend arent even the same as the options available to me.

For example, the website rather nebulously advises
"the recommended cluster size for a 128GB FAT32 partition is 32KB and the recommended cluster size for a 256GB partition is 64KB"
These cluster sizes are not even available in the list of options that GUIFormat provides
 
those options
GUIFormat gives me a number of options to for the Allocation Unit Size which are;
512
1024
2048
4096
8192
16384
32768
65536
 
Last edited by a moderator:
@dodo,
I guess your web searching result are vague because, in my opinion and experience, it makes little difference.
certainly none that I have noticed in the real world.

normally you have no idea the mix of file sizes you will have and setting an allocation to suit one category of files will render another category worse off.
even in your case where you know what the majority of files will be, you still show a large size range potential.

so the gamble is, set it low and have many I/O's per file management, or set it high but have unused excesses.

for me, there is no right or wrong answer.

your best bet will be to set it to one allocation, trail it for a few hours/days, then pick another setting and see if you notice any difference.
(yep, it'll suck having to reformat and recopy the files but there you have it)

then to murky the waters even more, factors like SSD vs HDD, FAT vs NTFS, internal vs external, SATA vs USB - and the size allocation starts to be the smallest of your concerns. :)
 
Usually for large drives you should use the default Allocation size of 4k or 4096 bytes when formatting for Fat32..
 
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Any update for us dodohelp? This thread will be closed if not replied to within 48hrs.
 
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