Best options to create and mount an ext4 volume containing > 10M files in one directory

What are the appropriate options to mkfs and mount for an ext4 filesystem with a folder containing >10 million files for read access?

What I have so far:

umount /media/dirsizetest
mkfs.ext4 -L DIRSIZETEST -E lazy_itable_init=1 -E lazy_journal_init=1 -m 1 /dev/sda1
mount -t ext4 -o nodiratime /dev/sda1 /media/dirsizetest

Some context is in order. I'm doing a slightly (OK, very) crazy experiment involving seeing how different file systems perform with a single folder filled with millions of small files. Eventually I'll be filling a 1TB drive to capacity doing this (I told you it was a crazy experiment!).

The access patten is something along these lines:

Recreate the volume from scratch (using mkfs) and mount it.
Create a sub-directory, fill it with N files in sequence (named 1...N)
    (where N can be up to 2^63)
Read all files in order
Read all files in random order
Print how it takes

My natural habitat is the Windows NTFS world, and the number of options to mount and mkfs are a bit daunting. So I'm looking for guidance on what options are likely to shoot my performance in the foot.

I'm working in a 64 bit Ubuntu 12.04 desktop environment.

Solution 1:

Attention: Security advice

These instructions are UNSAFE and should not be used in production environment without precautions.

For example a battery backed RAID card can help to decrease risks.

Use at own risk

If you just like it as a test environment I'd recommend the ext4 options

noatime,data=writeback,barrier=0,nobh,errors=remount-ro

This

• disables accesstimes on read
• writes metadata lazily
• disables the enforcing of proper on-disk ordering of journal commits
• tries to avoid associating buffer heads
• remounts read only on error

for mkfs.ext4 I could only find the option

dir_index
    Use hashed b-trees to speed up lookups in large directories.

usefull

Solution 2:

Some research I did found the following links. Chris Perrin's answer provides a short list of options; these should provide additional reference material.

• Blog post in improve ext4 performance
• Kernel.org documentation for ext4
• man page for mkfs.ext4