Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!usc!apple!aux.support.apple.com!winders
From: winders@aux.support.apple.com (Scott Winders)
Newsgroups: comp.sys.mac.system
Subject: Re: Is there a limit on the number of files?
Message-ID: <52739@apple.Apple.COM>
Date: 11 May 91 01:20:35 GMT
References: <10173@castle.ed.ac.uk>
Sender: nntp@Apple.COM
Organization: Apple Computer, Inc.
Lines: 40

In article <10173@castle.ed.ac.uk> crs@castle.ed.ac.uk (C R Smart) writes:

> Is there a limit to the number of files which the mac can handle?  I
> have been warned that "funny things" happen when the number of files
> tops about 700.  I am a bit concerned as I have about 800 files at the
> moment.
> 
> Is there a limit?  Was there a limit?  If there is a limit, how to
> increase it?

The following is true for System Software 6.0.x and System 7:

It is sometimes noted that HFS is limited to 64,000 files per volume. This
is not strictly correct, though it may be true in practice.
 
A count of the total number of files and directories on the volume is
maintained, as a LongInt, in the MDB (block 2). Directory IDs are also
LongInts. This limits the number of files and folders on the volume to
2^32-1 (roughly 4.3 billion). That many folders could be created as long
as there's room on the volume to hold the expanding catalog B*-Tree. Because
each file occupies at least one allocation block, all of at most 65,536
allocation blocks (also numbered by Integers) will be allocated just before
that many files are written on the volume, so the limit of 64,000 files will
turn out to be close to the practical limit.
 
There is another limitation imposed: a directory's valence is an Integer,
and, furthermore, on GetCatInfo requests, any negative number in the
ioFlIndex field is interpreted as a request for information on the
directory itself. So, while HFS allows the creation of up to 65,536 files
in each directory, all of which can be accessed by name, only 32,767 can be
enumerated -- a real limitation on folder contents. In practice, the user's
patience will run out well before this many items can be enumerated.
 
Finally, all computations on file sizes are performed using LongInts, so
there's no practical limit on the size of an individual file -- though the
actual limit is about two gigabytes.

Scott Winders
internet: winders@aux.support.apple.com
AppleLink: winders.s@applelink.apple.com