- EXT3 supports 32,000 subdirectories.
- EXT4 supports 64,000...
- I've read about people having millions of subdirectories on the XFS filesystem, but can't find an exact value referenced anywhere.
How many subdirectories does the XFS filesystem support?
I do not think there is a hard limit except for the maximum file size of 2^64-1 bytes. But there would be a couple of "soft" limits - searching a large directory might become inefficient due to high CPU and/or memory intensity.
From the XFS project site at SGI (a bit aged already):
There are of course other practical considerations....like the total length of a filename allowed which may be far less than the number of subdirectories allowed.
Anyway, a subdirectory is just a file anyway, so isn't the absolute maximum number of subdirectories is theoretically the max number of i-nodes on a specific filesystem?