Hardware and performance

I have a Moodle installation that I intend to use ,for 600 concurrent users and my Server specs are 16GB Ram and 8 processor cores. I would appreciate it if you can look at my my.cnf settings below and make recommendations on how best to optimise the system. I have not gone above 300 concurrent users taking a quiz at the same time and I have Database failure warnings.

Thanks much! 

interactive_timeout=600

key_cache_block_size=4096

max_heap_table_size=132M

max_join_size=1000000000

max_allowed_packet=268435456

open_files_limit=10000

query_cache_size=200M

thread_cache_size=100

tmp_table_size=532M

wait_timeout=3800

max_user_connections=2000

myisam_recover_options=FORCE

innodb_file_per_table=1

innodb_flush_log_at_trx_commit=0

innodb_purge_threads=1

innodb_support_xa=0

innodb_thread_concurrency=40

table_open_cache=328

innodb_buffer_pool_size=200000000

innodb_file_format = barracuda

innodb_large_prefix

innodb_file_per_table = 1