Erratic behaviour -- very fast then very slow

Hi, need some advice here. I'm supporting 1 popular website (up to 600+ users during peak) with 2 servers - 1 httpd connected remotedly to 1 mysql. Recently I'm getting very erratic behaviour. Pages sometimes load very fast and somethings very slow. When I observe top on both servers, I'll see cpu load climbing then suddenly drops and rise again like rollar coster. It happens during peak and offpeak hours! Occassionally I'll get lost connection to mysql as well. I'm not sure what's wrong. Can anyone advise? Below are my stats:

httpd.conf

Timeout 300
KeepAlive Off
MaxKeepAliveRequests 100
KeepAliveTimeout 2
MinSpareServers 20
MaxSpareServers 35
StartServers 15
MaxClients 800
MaxRequestsPerChild 50
mysqladmin variables

back_log 50
basedir /
binlog_cache_size 32768
bulk_insert_buffer_size 8388608
character_set latin1
character_sets latin1 big5 czech euc_kr gb2312 gbk latin1_de sjis...
concurrent_insert ON
connect_timeout 120
convert_character_set
datadir /var/lib/mysql/
default_week_format 0
delay_key_write ON
delayed_insert_limit 100
delayed_insert_timeout 300
delayed_queue_size 1000
flush OFF
flush_time 0
ft_boolean_syntax + -><()~*:""&|
ft_min_word_len 4
ft_max_word_len 254
ft_max_word_len_for_sort 20
ft_stopword_file (built-in)
have_bdb NO
have_crypt YES
have_innodb DISABLED
have_isam YES
have_raid NO
have_symlink YES
have_openssl NO
have_query_cache YES
init_file
innodb_additional_mem_pool_size 1048576
innodb_buffer_pool_size 8388608
innodb_data_file_path
innodb_data_home_dir
innodb_file_io_threads 4
innodb_force_recovery 0
innodb_thread_concurrency 8
innodb_flush_log_at_trx_commit 1
innodb_fast_shutdown ON
innodb_flush_method
innodb_lock_wait_timeout 50
innodb_log_arch_dir
innodb_log_archive OFF
innodb_log_buffer_size 1048576
innodb_log_file_size 5242880
innodb_log_files_in_group 2
innodb_log_group_home_dir
innodb_mirrored_log_groups 1
innodb_max_dirty_pages_pct 90
innodb_max_purge_lag 0
innodb_table_locks ON
interactive_timeout 250
join_buffer_size 1044480
key_buffer_size 16777216
language /usr/share/mysql/english/
large_files_support ON
license GPL
local_infile ON
locked_in_memory OFF
log OFF
log_update OFF
log_bin OFF
log_slave_updates OFF
log_slow_queries ON
log_warnings 2
long_query_time 3
low_priority_updates OFF
lower_case_file_system OFF
lower_case_table_names 0
max_allowed_packet 33553408
max_binlog_cache_size 4294967295
max_binlog_size 1073741824
max_connections 800
max_connect_errors 10
max_delayed_threads 20
max_insert_delayed_threads 20
max_heap_table_size 16777216
max_join_size 4294967295
max_relay_log_size 0
max_seeks_for_key 4294967295
max_sort_length 1024
max_user_connections 0
max_tmp_tables 32
max_write_lock_count 4294967295
myisam_max_extra_sort_file_size 268435456
myisam_max_sort_file_size 2147483647
myisam_repair_threads 1
myisam_recover_options OFF
myisam_sort_buffer_size 67108864
net_buffer_length 16384
net_read_timeout 30
net_retry_count 10
net_write_timeout 60
new OFF
open_files_limit 4010
pid_file /var/lib/mysql/odie.sgboyx.com.pid
log_error
port 3306
protocol_version 10
query_alloc_block_size 8192
query_cache_limit 1048576
query_cache_size 33554432
query_cache_type ON
query_prealloc_size 8192
range_alloc_block_size 2048
read_buffer_size 2093056
read_only OFF
read_rnd_buffer_size 262144
rpl_recovery_rank 0
server_id 1
slave_net_timeout 3600
skip_external_locking ON
skip_networking OFF
skip_show_database OFF
slow_launch_time 2
socket /var/lib/mysql/mysql.sock
sort_buffer_size 2097144
sql_mode 0
table_cache 1024
table_type MYISAM
thread_cache_size 128
thread_stack 126976
tx_isolation REPEATABLE-READ
timezone SGT
tmp_table_size 33554432
tmpdir /tmp/
transaction_alloc_block_size 8192
transaction_prealloc_size 4096
version 4.0.22-standard-log
version_comment Official MySQL RPM
version_compile_os pc-linux
wait_timeout 1200
I've renice mysql to the highest priority on mysql server and also shutdown exim, eximstats, imap, pop and ftp on that server.

 

 

 

 

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