UNIX for Dummies Questions & Answers

Hi,

Does Linux/Solaris has any limit on folder size or number of files per folder?

Thanks
Bache Gowda

I can speak with some authority about Solaris and I'm sure that linux is very similiar.

In the Unix world, we use the term directory rather than folder. The difference is important. You literally put a document in a folder, but you only put the name of a document in a directory. Once a document is in a folder, it can't also be in a second folder. But you can list the name of a document in as many directories as you want.

To fit a file into a directory, we must have room for the name of the file. But the size of the file is irrelevant.

In Unix, a directory contains a name and a inode number for every file in it. So how big can this list be? The max file size comes into play here. After all, a directory is a file itself. Under early versions of Solaris, the max file size was 2 Gb. Recent versions of Solaris now support large files. Large files are 8,589,934,592 Gb in theorical length but there is no way to attach enough disk drives to a computer to allow creation of such a large file.

But even with small files, if we say that a typical file name is 20 bytes long together with 4 bytes for the inode, then we can get 2147483648 /24 = 89,478,485 files in a directory. With smaller file names, you could up that a bit.

This however would be a very dumb thing to do. Directories are searched sequentially. Very large directories drag down system performance. I try to keep all of my directories under 1000 files.

The largest directory that I ever saw had about 130,000 files in it. Manipulating it was painful.