Try increasing your journal size (mke2fs -J size=400), and having a lot of RAM. When you say "having about 100M files", does that mean "need to be constantly accessing 100M files" or just "need to store a total of 100M files in this filesystem"?
Likely only 10M will be accessed at any time.
The system has 16G of RAM; getting 32G in the future is a possibility. Where do you get 128 + 32 from? Is 128 the inode size? this is running a 64bit os. Does that change the memory requirements?The former means you need to keep the whole working set in RAM for maximum performance, about 100M * (128 + 32) = 19GB of RAM. The latter is no problem, we have ext3 filesystems with > 250M files in them.
Thanks, I will try your suggestion. Sean