my zabbix server every noght going down by Housekeeper Processes

[khvn]

every night at specified time when housekeeper start to work my server going down (freeze everything like SSH,Console).
I Should restart manually my server then every thing going well till tomorrow night.
my zabbix log before going to freeze is ( housekeeper [deleted 1046147 hist/trends, 0 items/triggers, 70 events, 5320 problems, 0 sessions, 0 alarms, 3 audit items in 194.164540 sec, idle for 1 hour(s)])
my zabbix version is 3.4.15 and my MariaDB is 10.2.23
i have

Number of hosts (enabled/disabled/templates)	997	677 / 228 / 92
Number of items (enabled/disabled/not supported)	53462	33778 / 15722 / 3962
Number of triggers (enabled/disabled [problem/ok])	15573	9751 / 5822 [118 / 9633]

Required server performance, new values per second

393.92

i have 30 GB RAM and 24 core CPU (Intel(R) Xeon(R) CPU E5-2690 v3 @ 2.60GHz)
my database configuation is:

[server]
default_storage_engine         = InnoDB
innodb                         = FORCE
open_files_limit = 16384
innodb_buffer_pool_size = 20G
innodb_file_per_table
innodb_log_buffer_size         = 32M
innodb_log_files_in_group       = 2
innodb_log_file_size            =2G
innodb_max_dirty_pages_pct     = 10
innodb_open_files              = 16384
innodb_thread_concurrency       =       24
query_cache_size               =2048
query_cache_type               = 1
query_cache_strip_comments      =1
skip_name_resolve = 1
query_cache_limit = 1024M
performance_schema = ON
event_scheduler = on
expire_logs_days        = 14
innodb_open_files              = 8182
log-queries-not-using-indexes
innodb_buffer_pool_instances = 20
long_query_time = 25
lower_case_table_names = 1
max_connections        = 800
max_connect_errors     = 700
max_heap_table_size  = 32M
slow_query_log = 1
slow_query_log_file     = /var/log/mariadb/mariadb-slow.log
table_open_cache               = 500
thread_cache_size              = 980
tmp_table_size                 = 32M
[mysqld]
log_error = /var/log/mysql/error.log
[galera]
[embedded]
[mariadb]
[mariadb-10.2]

[epizarro]

check your DB IO wait