[CentOS] Question about optimal filesystem with many small files.

Wed Jul 8 22:53:50 UTC 2009
Les Mikesell <lesmikesell at gmail.com>

oooooooooooo ooooooooooooo wrote:
>> You can hash it and still keep the original filename, and you don't
>> even need a MySQL database to do lookups.
> There are an issue I forgot to mention: the original file name can be up top 1023 characters long. As linux only allows 256 characters in the file path, I could have a (very small) number of collisions, that's why my original idea was using a hash->filename table. So I'm not sure if I could implement that idea in my scenario.
>> For instance: example.txt ->
>> e7/6f/example.txt. That might (or might not) give you a better
>> performance.
> After a quick calculation, that could put around 3200 files per directory (I have around 15 million of files), I think that above 1000 files the performance will start to degrade significantly, anyway it would be a mater of doing some benchmarks.

There's C code to do this in squid, and backuppc does it in perl (for a 
pool directory where all identical files are hardlinked).  Source for 
both is available and might be worth a look at their choices for the 
depth of the trees and collision handling (backuppc actually hashes the 
file content, not the name, though).

   Les Mikesell
    lesmikesell at gmail.com