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Format exFat HD - Best Allocation Unit Size for Mac and Win

Started by lela , Sep 15 2021 06:59 PM

Format exFat external hard drive portable hard drive allocation unit size Mac Win PC Apple

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#1
lela

Posted 15 September 2021 - 06:59 PM

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17 posts

I'd appreciate anyone's advice or shared experience.

1) Does anyone know the minimum allocation unit size (AUS) - which I should select when I format an external Hard Drive (HD) to exFat ?

2) Do I need to do a full format when I format the HD to exFat? Or, is a quick format okay?

I am currently using PC (Win 7-10) - and I am planning to get a Mac so I want to format my backup HD to exFat.

PC (Win) AUS default = 256 Kb

Mac AUS default = 128 Kb or 64 Kb (does anyone know?)

I found very few answers when I 'researched' online. A couple of writers (not Apple reps) wrote that 128 Kb was the minimum for read/write on Mac OS - and thus, 128 Kb should be the AUS. Another couple of writers (not Apple reps) claimed that 64Kb is the default which will work as the AUS and that even 32Kb or less, should work.

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Also tagged with one or more of these keywords: Format, exFat, external hard drive, portable hard drive, allocation unit size, Mac, Win, PC, Apple

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