Home > Storage > PowerScale (Isilon) > Product Documentation > Storage (general) > PowerScale OneFS: Long Filename Support > Filename mangling
If a filename is too long for a particular protocol, OneFS automatically truncates the name to around 249 bytes with a hash that is appended to it, that can be used to consistently identify and access the file. This shortening process is referred to as “name mangling” in the OneFS lexicon, resulting in a mangled filename. For example, if a filename longer than 255 bytes is created and then returned to a directory listing over the NFSv3 protocol, the file’s mangled name will be presented. Any subsequent lookup operations that are performed on this mangled name resolve to the same file with the original long name.
Using the long-named .tmp file created in the previous example, when viewed from an NFSv3 client, this file is shortened to a 255-character mangled encoding:
# ls ./test/*.tmp
123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789#2c0b5*
The same file, viewed through a cluster’s SMB share from a Windows 10 client’s file explorer, also displays the same 255-character mangled-name truncation:
Filename extensions are lost when a name is mangled. For example, a Microsoft Word .docx long-named file will no longer appear as a .docx file after name mangling.