ext4 and extremely slow filesystem traversal

[Vincent Caron]

On 14/03/2013 21:57, Peter Grandi wrote:
>> This filesystem has no file owned by root and won't have
>> > any. I thought in this case -m0 would be a good idea.
> Why does it matter here that "no file owned by root"?
> 
> What has that got to do with the much greater difficulty to find
> contiguous space the fuller the filetree is?

  Because the man page says that reserved blocks are used to protect
root-level daemons from misbehaving would unprivileged programs try to
fill the disk. And uh, to avoid fragmentation, I missed that part.

  OTOH I monitor disk space and never let go past 95% block usage
without specific action (freeing inodes or enlarging filesystem). Would
I use -m5 and oversize my filesystems (because I sell the capacity, say
I sell 100GB then I need a 105GB blockdev), I would still monitor the
disk usage and take action before it's 100% filled up. But I'd end up
reserving more blocks without more guarantees that the -m0 case.

  So technically it looks wrong, but politically I'm not sure it's
stupid. Or is it ?