[OpenAFS] Maximum number of directory created under a volume?
Mon, 09 May 2005 21:50:03 -0400
On Tuesday, May 10, 2005 09:36:33 AM +0800 Alvin Chan
> Hi all,
> I would like to ask if there is a maximum number of directory that can be
> created under a volume. I've tried to created directories under a volume
> and the last one that can be created is the 64435th. And after that an
> error mesage of "Cannot create directory '/xxxx' : File too large". But
> there's certainly still lots of space left. So is 64435 the number limit
> and why is it so?
There is a limit to the number of entries that can be created in any given
directory. The limit depends on the length of the filenames; if they are
all sufficiently short, the limit is around 64K; longer filenames result in
This limit is imposed by the on-disk and on-the-wire structure of AFS
directories. Allowing a larger number of entries would require a change to
these structures, which would render them incompatible with existing
fileservers and clients. A transition to a new format is possible, but
will be a significant undertaking requiring that care be taken to maintain
as much backward compatibility as possible. We'll get there, eventually,
but it will take time.
I would suggest that if you have a directory containing on the order of 64K
entries, it is time to stop and reconsider your filesystem layout. While
there are certainly legitimate reasons to need that number of files in a
single directory, they are quite uncommon, and usually it is appropriate to
consider a deeper structure. Bear in mind that while AFS's directories are
hash tables, most other filesystems use linear directories, in which the
time required to locate, insert, or delete an entry in a directory that
size can be quite significant.
-- Jeffrey T. Hutzelman (N3NHS) <firstname.lastname@example.org>
Sr. Research Systems Programmer
School of Computer Science - Research Computing Facility
Carnegie Mellon University - Pittsburgh, PA