Pros and Cons of less files in a folder

[mattalexx]

I have a caching directory that holds images. The directory might at some point carry millions of images. Right now, I hold them like this:

/cache/images/0cbc65283c3385469b18d8ead375177b.jpg
/cache/images/0f6a8324e77936f281c176740e5d88df.jpg
/cache/images/1cb609c319a57f816b807172f8369cdb.jpg
/cache/images/2b6dc4d6135bd9808e4f60617cef287e.jpg
/cache/images/3d0d6c7ab1cae640977a2de52f56455b.jpg
/cache/images/6a9291311264b50563fda7fd61b29be0.jpg

But I've seen people do this:

/cache/images/0/c/0cbc65283c3385469b18d8ead375177b.jpg
/cache/images/0/f/0f6a8324e77936f281c176740e5d88df.jpg
/cache/images/1/c/1cb609c319a57f816b807172f8369cdb.jpg
/cache/images/2/b/2b6dc4d6135bd9808e4f60617cef287e.jpg
/cache/images/3/d/3d0d6c7ab1cae640977a2de52f56455b.jpg
/cache/images/6/a/6a9291311264b50563fda7fd61b29be0.jpg

I'm assuming that they do that so that there are less files per folder and it speeds up IO stuff a little. Am I right? If not, what's the real reason?

[cmuench]

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FAT aka FAT16

FAT, for File Allocation Table, is the successor to the original FAT12 filesystem that shipped with MS-DOS many, many years ago.
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Maximum disk size: 4 gigabytes
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Maximum file size: 4 gigabytes
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Maximum number of files on disk: 65,517
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Maximum number of files in a single folder: 512 (if I recall correctly, the root folder "/" had a lower limit of 128).
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FAT32
"There's no practical limit on the combined sizes of all the files in a folder, though there may be limits on the number of files in a folder."

FAT32 was introduced to overcome some of the limitations of FAT16.
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Maximum disk size: 2 terabytes
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Maximum file size: 4 gigabytes
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Maximum number of files on disk: 268,435,437
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Maximum number of files in a single folder: 65,534
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NTFS

NTFS, or "New Technology File System" introduced with Windows NT, is a completely redesigned file system.
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Maximum disk size: 256 terabytes
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Maximum file size: 256 terabytes
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Maximum number of files on disk: 4,294,967,295
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Maximum number of files in a single folder: 4,294,967,295



Linux has no limit that I could find. however if you are using a journaling file system one would think it would slow down to have to find the file.

[mattalexx]

Thanks. That was helpful (and kind of interesting). There's CentOS on ext3 on the server. I guess I will try it. Won't hurt.