Do modern computers still need the kind of routine defragmentation procedures that older computers called for? Read on to learn about fragmentation and what modern operating systems and file systems do to minimize performance impacts.

今天的問答環節是由SuperUser提供的，SuperUser是Stack Exchange的一個分支，它是一個由Q&a網站組成的社群驅動分組。

問題

超級使用者讀者Simon Sheehan對現代硬碟的碎片整理狀態很好奇：

As a part of regular Windows maintenance, I defragment my hard drive. But why does the hard drive fragment on NTFS and FAT* systems? Apparently EXT* does not, why is this? Should I also be defragmenting my USB drives?

讓我們看看投稿人的一些答案來調查西蒙的問題。

答案

超級使用者貢獻者Daniel R.Hicks提出了一個問題：

Fragmentation is not the issue it was 30 years ago. Back then you had hard drives that were scarcely faster than floppies, and processor memory sizes that were minuscule. Now you have very fast drives and large processor memories, and sometimes substantial buffering on the hard drive or in the controller. Plus sector sizes have gotten larger (or files are allocated in larger blocks) so that more data is inherently contiguous.

Operating systems have gotten **arter as well. Whereas DOS 1.x would have fetched each sector from disk as it was referenced, a modern OS is able to see that you have a file open for sequential access and can reasonably predict that you’ll be fetching additional sectors once you’ve c***umed those you have now. Thus it can “pre-fetch” the next several (dozen) sectors.

And any more it’s often better to not have a file contiguous. On a (large) system where the file system is spread across multiple drives a file can actually be accessed faster if it is “spread” as well, since multiple disks can be seeking the file simultaneously.

I defragment every 2-3 years, whether my box needs it or not.

[I’ll add that the important thing is not so much whether the data on the disk gets defragmented as whether the free space does. FAT was terrible at this — unless you defragged things kept getting worse and worse until there were no two contiguous blocks of free space. Most other schemes can coalesce free space and allocate pieces in a somewhat “**art” fashion so the fragmentation reaches a certain threshold and then stabilizes, rather than getting worse and worse.]

Journeyman Geek添加了關於Linux檔案系統的以下資訊：

ALL file systems fragment. ext and other Linux file systems fragment less due to the way they’re designed – to quote Wikipedia regarding the Linux Network Administrators’ Guide:

Modern Linux filesystem(s) keep fragmentation at a minimum by keeping all blocks in a file close together, even if they can’t be stored in c***ecutive sectors. Some filesystems, like ext3, effectively allocate the free block that is nearest to other blocks in a file. Therefore it is not necessary to worry about fragmentation in a Linux system.

I’d note though that ext4 has online defragmentation so eventually fragmentation IS an issue, even with Linux file systems.

Windows file systems have their clusters placed wherever there’s space to put them, and defrag runs around and replaces them. With Linux, files are preferentially placed where there’s enough space.

I’d note though, Windows 7 has scheduled defragmentation runs, so it isn’t really necessary to run defrag manually.

最初的一個問題沒有解決，那就是你是否應該整理你的快閃記憶體驅動器。碎片整理是一個非常讀/寫密集型的過程，應該避免在固態儲存裝置上，如快閃記憶體驅動器和固態磁碟（ssd）。有關碎片整理、檔案系統和SSD的更多資訊，請參閱以下HTG文章：

• HTG解釋說：你真的需要整理你的電腦嗎？
• HTG解釋道：什麼是固態硬碟，我需要知道什麼？
• HTG解釋：為什麼Linux不需要碎片整理

有什麼要補充的解釋嗎？在評論中發出聲音。想從其他精通技術的Stack Exchange使用者那裡瞭解更多答案嗎？在這裡檢視完整的討論主題。