FORMAT Ổ ĐĨA CỨNG NÊN ĐẶT ALLOCATION UNIT SIZE LÀ GÌ

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Jason FitzpatrickSenior Smart trang chủ Editor

Jason Fitzpatrick is the Senior Smart home Editor at How-To Geek. He has over a decade of experience in publishing and has authored thousands of articles at How-To Geek, review Geek, LifeSavvy, và Lifehacker. Jason served as Lifehacker"s Weekend Editor before he joined How-To Geek. Read more...

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In addition khổng lồ asking for the file system you’d like to use, disk formatting tools will also ask for an “Allocation unit size”. What does this mean and what value should you select?

Today’s Question & Answer session comes to lớn us courtesy of SuperUser—a subdivision of Stack Exchange, a community-driven grouping of Q&A website sites.


The Question

SuperUser reader Andrew Keeton is curious about what exactly he’s supposed to lớn put in the allocation section when formatting a drive. He writes:

I’m formatting a 1TB external hard drive as NTFS. This drive is mainly meant for storing truyền thông such as music và video.

What should I choose for the allocation unit kích cỡ setting? The options range from 512 bytes lớn 64K. Are there any guidelines that I might apply lớn other drive types? Should I stop poking around và just leave it at “default?”

While the mặc định setting is usually the best choice for most users, let’s dig a little deeper.

The Answers

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SuperUser contributors Jonathan & Andrew offer some insight. Jonathan writes:

If you are a “Standard User” by Microsoft’s definition, you should keep the mặc định 4096 bytes. Basically, the allocation unit size is the block kích cỡ on your hard drive when it formats NTFS. If you have lots of small files, then it’s a good idea to lớn keep the allocation kích cỡ small so your harddrive space won’t be wasted. If you have lots of large files, keeping it higher will increase the system performance by having less blocks to seek.

But again, nowadays hard drive capacity is getting higher và higher it makes small difference by choosing the right allocation size. Suggest you just keep the default.

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Also keep in mind that the majority tệp tin are relatively small, larger files are large in kích cỡ but small in units.

Andrew expands upon Jonathan’s answer with:

In terms of space efficiency, smaller allocation unit sizes perform better. The average space wasted per file will be half the chosen AUS. So 4K wastes 2K per file và 64K wastes 32K. However, as Jonathon points out, modern drives are massive & a little wasted space is not worth fussing over and this shouldn’t be a determining factor (unless you are on a small SSD).

Compare 4K vs 64K average case waste (32K-2K = 30K), for 10,000 files that only comes out khổng lồ 300,000KB or around 300MB.

Instead think about how the OS uses space. Let’s say you have a 3K file which needs lớn grow 2K. With a 4K AUS the data needs to lớn be split over two blocks – and they may not be together so you get fragmentation. With a 64K AUS there are a lot fewer blocks to keep track of và less fragmentation. 16x the block kích thước means 1/16th the number of blocks lớn keep track of.

For a truyền thông disk where you photos, music and videos are stored, every tệp tin is at least 1MB I use the biggest AUS. For a windows boot partition I use the Windows default (which is 4K for any NTFS drive smaller than 16TB).

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To find out what the cluster size is on an existing disk:

fsutil fsinfo ntfsinfo X:

Have something to địa chỉ to the explanation? Sound off in the the comments. Want to lớn read more answers from other tech-savvy Stack Exchange users? check out the full discussion thread here.


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Jason FitzpatrickJason Fitzpatrick is the Senior Smart home Editor at How-To Geek. He has over a decade of experience in publishing và has authored thousands of articles at How-To Geek, đánh giá Geek, LifeSavvy, and Lifehacker. Jason served as Lifehacker"s Weekend Editor before he joined How-To Geek. Read Full Bio »