What is the limit of EXT4, what i found is only EXT3, and other links only suppositions and not a real number?
Can you please provide me: max number per directory, max size?
It depends upon the MKFS parameters used during the filesystem creation. Different Linux flavors have different defaults, so it's really impossible to answer your question definitively.
Follow-up on @Curt's answer. The creation parameters can determine the number of inodes, and that's what can limit you in the end. df's -i switch gives you inode info.
(env)somesone@somewhere:/$ df -iT
Filesystem Type Inodes IUsed IFree IUse% Mounted on
/dev/root ext4 25149440 612277 24537163 3% /
devtmpfs devtmpfs 3085602 1418 3084184 1% /dev
none tmpfs 3086068 2 3086066 1% /sys/fs/cgroup
none tmpfs 3086068 858 3085210 1% /run
none tmpfs 3086068 1 3086067 1% /run/lock
none tmpfs 3086068 1 3086067 1% /run/shm
none tmpfs 3086068 4 3086064 1% /run/user
This is a Linode box BTW, so it's virtualized environment. The number I look at is 24537163, that's how many free inodes the root fs has. Note, that more than 10K files in a directory can cause difficulties for many tools. 100K can be really hard on utilities.
来源：https://stackoverflow.com/questions/17537471/what-is-the-max-files-per-directory-in-ext4