Ask HN: Stretching Linux server limits?

Few details about our server(Virtual Box Guest OS) setup and info: - We have ~30,000 home directories and approaching 32768 users. - Fedora 14 Kernel : 2.6.35.14-106.fc14.i686 - 30 GB total disk space. - /etc/group and /etc/passwd is ~1.5M and /etc/shadow is 3.6M - 900K free inodes on /home and 16G free disk-space. - /home formatted as 'ext4', which overcomes 32768 sub-directories limits by ext3. This shared environment protected with : - Linux Quota - For individual users and all users belong to same Secondary group (now single group has ~30,000 user) - Group Quota is applied too. - SELinux roles for each user - Pam.d and resource limits for each user. Few things we planned a year ago - but not yet deployed. - openLdap - Migrate user home directories to NFS or distributed storage. - Migrate to 64bit-CentOS.6 or 7. (just couple of guys running this www.webminal.org project - above 3 items may get delayed by 6 more months) So the question is, since we are approaching 32768 number. Do you think it may affect server? like having 32,768 user to single group or any other possible issue? (already we see few strange behavior with pkill -u <username> not responding properly sometimes). Issues that may come-up when reach limits, have you encountered them? If so please share. thanks!