Filipe Brandenburger wrote:
Found it! It's not related to CentOS 4 or 5 (I found a C4 machine in which small files took 8kb of diskspace and a C5 machine in which small files took 4kb). It's related to SELinux being enabled or not. Casually most of my C4 machines had SELinux disabled and most of my C5 have it enabled. Now I dug out some machines with the opposite config and I checked it out.
I believe if SELinux is enabled, it will use extended attributes to store the file's SELinux context (you can see it with "ls -Z", for some reason you cannot see it with "getfattr -d", I was expecting that to be possible). I guess when the file has extended attributes it will use an additional block to store them. That basically doubles the storage requirements if you have millions of tiny files...
It shouldn't be doing that. Was this an old filesystem, originally created without security attributes? What does tune2fs show for the inode size? On my Fedora 10 laptop, where the filesystem was originally set up with SELinux attributes, the inode size is 256 bytes and the security attributes are stored in the inode itself. On my systems without SELinux, the inode size is 128 bytes, so the penalty is the additional 128 bytes per inode, not 4K per file.
If you run debugfs on the partition and use its 'stat' command you can see where the security attributes are stored.
AFAIK if you are running SELinux there is no way to keep it out of any filesystem capable of supporting extended attributes.