how are files stored on disk?

Brad Fitzpatrick brad at
Wed Jun 7 00:07:24 UTC 2006

On Tue, 6 Jun 2006, Eric Lambrecht wrote:

> Chuck Remes wrote:
> > 1. How are files stored on disk and in what directory structure? Do
> > they have meaningful names or do they use a unique hash as their name?
> Their filename is their 'fid', which is the unique number that
> represents the file in the database.

To be clear for Chuck...

Unique number that represents a _unique instance_ of a file.  If a file
has a name ("my_document"), a fid is one immutable version of that file.
If you later upload "my_document" again, it gets a new fid, and the file
-> fid map is updated.  The old "my_document" (fid 100) is now
"my_document" (fid 205).

This is great for backups:  just rsync your mog storage node roots
somewhere, and you'll only get new stuff, never destroying old versions.

> We easily store hundreds of thousands of files without problems.

Many million here, but we have small files where you have less (but
larger) ones.

- Brad

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