[svnbook commit] r2925 - trunk/src/en/book

Ben Collins-Sussman sussman at red-bean.com
Sat Dec 15 21:32:41 CST 2007

On Dec 15, 2007 8:27 PM, cmpilato <noreply at red-bean.com> wrote:

> +          more files into these two directories, and over time, the
> +          number of these files in each directory can grow to be quite
> +          large.  Unfortunately, this can cause performance problems
> +          on many operating systems.

In the whole three years FSFS has been out and about, nobody has
*ever* reported a performance problem with the original "all revs in
one directory" design.  Not gcc, not gnome or kde, nor any other huge
project with tens of thousands of revisions.

As I understand it, the only reason malcolmr wrote this feature is
because he discovered that certain implementations of NFS were unhappy
at too many files in one directory, and the sharding sped things up a
lot.  So things sort of played out according to ghudson's original
statement:  "as soon as someone complains and demonstrates this is a
problem, I'll go ahead and shard it".  It took three years before
someone complained.

The point is:  I think it's misleading to say that the original FSFS
format can "cause performance problems on many operating systems".
It's more like "has been observed to cause performance problems on
certain network-based filesystems."

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