在一个目录中保存多少文件有关系吗?如果是，一个目录中有多少文件是太多的，拥有太多文件的影响是什么?(这是在Linux服务器上。)
Background: I have a photo album website, and every image uploaded is renamed to an 8-hex-digit id (say, a58f375c.jpg). This is to avoid filename conflicts (if lots of "IMG0001.JPG" files are uploaded, for example). The original filename and any useful metadata is stored in a database. Right now, I have somewhere around 1500 files in the images directory. This makes listing the files in the directory (through FTP or SSH client) take a few seconds. But I can't see that it has any effect other than that. In particular, there doesn't seem to be any impact on how quickly an image file is served to the user.
我想过通过创建16个子目录来减少图像的数量:0-9和a-f。然后我将根据文件名的第一个十六进制数字将图像移动到子目录中。但是除了偶尔通过FTP/SSH列出目录之外，我不确定这样做是否有任何理由。
我在一个ext3目录中有超过800万个文件。Libc readdir()， find, ls和本线程中讨论的大多数其他方法都使用它来列出大型目录。
ls和find在这种情况下很慢的原因是readdir()一次只读取32K的目录条目，所以在慢磁盘上需要很多很多次读取才能列出一个目录。这个速度问题有一个解决方案。我在http://www.olark.com/spw/2011/08/you-can-list-a-directory-with-8-million-files-but-not-with-ls/上写了一篇非常详细的文章
关键是:直接使用getdings()——http://www.kernel.org/doc/man-pages/online/pages/man2/getdents.2.html，而不是任何基于libc readdir()的方法，这样在从磁盘读取目录条目时就可以指定缓冲区大小。
上面的大多数答案都没有说明，对于最初的问题，没有“一刀切”的答案。
In today's environment we have a large conglomerate of different hardware and software -- some is 32 bit, some is 64 bit, some is cutting edge and some is tried and true - reliable and never changing.
Added to that is a variety of older and newer hardware, older and newer OSes, different vendors (Windows, Unixes, Apple, etc.) and a myriad of utilities and servers that go along.
As hardware has improved and software is converted to 64 bit compatibility, there has necessarily been considerable delay in getting all the pieces of this very large and complex world to play nicely with the rapid pace of changes.
恕我直言，没有一种方法可以解决问题。解决办法是研究各种可能性，然后通过反复试验找到最适合你特定需求的方法。每个用户必须确定什么适合他们的系统，而不是使用千篇一律的方法。
I for example have a media server with a few very large files. The result is only about 400 files filling a 3 TB drive. Only 1% of the inodes are used but 95% of the total space is used. Someone else, with a lot of smaller files may run out of inodes before they come near to filling the space. (On ext4 filesystems as a rule of thumb, 1 inode is used for each file/directory.)
While theoretically the total number of files that may be contained within a directory is nearly infinite, practicality determines that the overall usage determine realistic units, not just filesystem capabilities.
我希望以上所有不同的答案都能促进思考和解决问题，而不是成为进步的不可逾越的障碍。
