Maximum Number of entries in a directory

[Bill Campbell]

On Wed, Sep 20, 2006, Fairlight wrote:
>Simon--er, no...it was Scott Walker--said:
>> Any opinions as to the maximum number of entries you can have in a
>> directory before you have a severe degradation in performance?
>
>About 500.

At one point SCO systems had a hard limit of 999 directories in a
directory.  I ran into this on a 3.2v4.2 system in 1995 when an ISP
customer hit 1,000 customers in their /home directory.  This may have been
a limit on the top directory of a mounted file system.

>> Is Linux different than SCO in this regard?
>
>It's filesystem dependant, but I think most of the 32bit fs's will be
>similar.  It's at the point where you hit double dereferencing of inodes
>that the performance drops like a stone.

The newer file *NIX systems handle things with btrees which have basically
eliminated the horrible performance degradation found fifteen or twenty
years ago.  We commonly see user's Maildir folders with 10s of thousands of
messages without noticeable degradation.

We generally use ext3 files systems for Linux root directories, and xfs for
non-root file systems.  I avoid the Reiserfs like the plague having lost
several file systems after power outages and other abnormal shutdowns.

Bill
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