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Thank you for posting the WTF-16 document. Very relevant for OP. It's an old problem that people on different OS's need to access the same filesystem, particul

by ripe 2y ago

Thank you for posting the WTF-16 document. Very relevant for OP. It's an old problem that people on different OS's need to access the same filesystem, particularly Windows clients versus UNIXy clients. While UNIX filesystems traditionally accept any sequence of bytes except slash and NUL, and treat "." and ".." specially, Windows filesystems have had many additional restrictions on valid filenames, e.g., a list of "reserved names" that should not be used, short and long names, and case-insensitive names [1]. The NetApp filer, a NAS storage appliance, runs a specialized OS called Data ONTAP, which maintains a special on-disk representation called WAFL to enable this. WAFL is famous for its copy-on-write representation for file contents. [3] But in practice, most people in the real world are affected by its treatment of filenames. It's useful to take a look at how it solves these problems. The NAS presents the same set of files both as an NFS volume for UNIXy clients, as well as a CIFS volume for Windows clients. It does this by enhancing the directory entries with additional information and configuration features to satisfy both requirements. For typical problems and what features they offer to solve them, see their documentation page about naming files and paths [2]. [1] https://learn.microsoft.com/en-us/windows/win32/fileio/naming-a-file https://learn.microsoft.com/en-us/windows/win32/fileio/namin... [2] https://docs.netapp.com/us-en/ontap/nfs-admin/multi-byte-file-directory-qtree-names-concept.html https://docs.netapp.com/us-en/ontap/nfs-admin/multi-byte-fil... [3] Dave Hitz, "File System Design for an NFS File Server Appliance", https://www.cs.princeton.edu/courses/archive/fall17/cos318/readings/netapp.pdf https://www.cs.princeton.edu/courses/archive/fall17/cos318/r...

p_ing 2y ago
NTFS has the same two restrictions that many UNIX file systems have, NUL and slash. The APIs, Win32 in the case of [1], have further restrictions. If you want you can use a different API/personality and write whatever value you'd like (sans NUL and /) provided said personality has no limits -- NTFS does no validation itself. In practice, Win32 being the default personality makes said plethlora of restrictions true, but it isn't a "filesystem" limitation, rather an API restriction. A nuanced if unimportant difference.
sumtechguy 2y ago
If you want to subtly break a windows install you can use setCaseSensitiveInfo with fsutil. It turns on/off case sensitivity for a directory. There is also a similar set of options for samba shares which comes with interesting tradeoffs for speed of reading a directory list.

by ripe 2y ago

p_ing 2y ago

NTFS has the same two restrictions that many UNIX file systems have, NUL and slash. The APIs, Win32 in the case of [1], have further restrictions. If you want you can use a different API/personality and write whatever value you'd like (sans NUL and /) provided said personality has no limits -- NTFS does no validation itself. In practice, Win32 being the default personality makes said plethlora of restrictions true, but it isn't a "filesystem" limitation, rather an API restriction. A nuanced if unimportant difference.

sumtechguy 2y ago

If you want to subtly break a windows install you can use setCaseSensitiveInfo with fsutil. It turns on/off case sensitivity for a directory. There is also a similar set of options for samba shares which comes with interesting tradeoffs for speed of reading a directory list.