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.

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问题

超级用户读者Simon Sheehan对现代硬盘的碎片整理状态很好奇：

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?

让我们看看投稿人的一些答案来调查西蒙的问题。

答案

超级用户贡献者Daniel R.Hicks提出了一个问题：

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添加了关于Linux文件系统的以下信息：

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.

最初的一个问题没有解决，那就是你是否应该整理你的闪存驱动器。碎片整理是一个非常读/写密集型的过程，应该避免在固态存储设备上，如闪存驱动器和固态磁盘（ssd）。有关碎片整理、文件系统和SSD的更多信息，请参阅以下HTG文章：

• HTG解释说：你真的需要整理你的电脑吗？
• HTG解释道：什么是固态硬盘，我需要知道什么？
• HTG解释：为什么Linux不需要碎片整理

有什么要补充的解释吗？在评论中发出声音。想从其他精通技术的Stack Exchange用户那里了解更多答案吗？在这里查看完整的讨论主题。