High load on MySQL and I/O Wait

Nabbello

Active Member
Nov 9, 2016
39
5
58
italy
cPanel Access Level
Root Administrator
Hello i'm facing high I/O wait on my cPanel server with 280 accounts.

I think the cause will be Mysql, what do you think about my configuration?

Raid and disk performance are ok and the server have no performance issues atm.

Server Spec:
8 Core CPU E3-1275 v6
64GB DDR4 ECC
/home raid 1 with 2 SSD NVME 512 GB
/home2 raid 1 with 2 SSD Datacenter 960gb

My sar:

Code:
11:00:02 AM     CPU     %user     %nice   %system   %iowait    %steal     %idle
11:10:01 AM     all     34.07      1.46      5.63      2.66      0.00     56.18
11:20:01 AM     all     32.64      1.11      5.45      2.74      0.00     58.07
11:30:01 AM     all     34.93      1.33      5.78      2.64      0.00     55.33
11:40:01 AM     all     33.08      1.37      5.78      2.49      0.00     57.28
11:50:02 AM     all     36.19      2.18      6.37      2.78      0.00     52.49
12:00:01 PM     all     28.81      1.06      5.14      2.98      0.00     62.01
12:10:01 PM     all     31.08      1.75      5.41      3.84      0.00     57.92
12:20:01 PM     all     33.00      1.36      5.41      2.96      0.00     57.28
12:30:01 PM     all     34.27      1.22      5.54      2.66      0.00     56.31
12:40:01 PM     all     26.36      1.29      4.66      2.98      0.00     64.71
12:50:01 PM     all     30.49      1.77      5.40      2.73      0.00     59.60
My my.cnf

[client-server]
!includedir /etc/my.cnf.d
Code:
[mysqld]
innodb_flush_method=O_DSYNC
event_scheduler=ON
log-error = /var/lib/mysql/titanium.err
performance-schema=0
default-storage-engine=MyISAM
datadir=/var/lib/mysql
local-infile=0
innodb_file_per_table=1
innodb_buffer_pool_size=28G

query_cache_type=1
max_user_connections=100
max_connections=300
interactive_timeout=300
wait_timeout=300
connect_timeout=100
thread_cache_size=128
key_buffer_size=1024M
join_buffer_size=16M
max_connect_errors=20
max_allowed_packet=268435456
open_files_limit=50000
sort_buffer_size=48M
read_buffer_size=48M
read_rnd_buffer_size=4M
myisam_sort_buffer_size=128M
server_id=1
slow_query_log=1
slow_query_log_file=/var/log/mysql-slow-queries.log
long_query_time=2
collation_server=latin1_general_ci
sql_mode = "NO_ENGINE_SUBSTITUTION"


query_cache_size=5M
table_open_cache=15000
table_definition_cache=-1
performance_schema=on
innodb_log_file_size=15G
tmp_table_size=30M
max_heap_table_size=30M


[mysqldump]
max_allowed_packet=128M

[mysql]
no-auto-rehash
#safe-updates

[isamchk]
key_buffer_size=128M
sort_buffer_size=128M
read_buffer_size=32M
write_buffer_size=32M

[myisamchk]
key_buffer_size=128M
sort_buffer_size=128M         
read_buffer_size=32M
write_buffer_size=32M

[mysqlhotcopy]
interactive_timeout
 
Last edited by a moderator:

cPRex

Jurassic Moderator
Staff member
Oct 19, 2014
10,360
1,632
363
cPanel Access Level
Root Administrator
Hey there! There isn't enough data here to determine anything about the load or the wait times on the machine. If you suspect MySQL is the culprit, I'd recommend checking the output of this command:

Code:
mysqladmin proc status
as that will show if MySQL has any slow queries or other potential problems. If so, you may be able to optimize MySQL, but if not, the I/O wait could be something else completely.