确定慢CentOS 6 Apache服务器的问题

Question

Background: I have 2 servers - 1 Apache server and 1 MySQL server running CentOS 6. The web server connects to the MySQL server via a private IP behind the router. Both have /etc/hosts.allow/deny setup, and iptables is limited to specific ports and IP's being able to access they system on port 22 and/or 3306. Port 80 and 443 are open to all on the web server.

Starting last week after a yum update the web server is extremely slow, on occasion, serving data. Some Javascript files served locally take 30 seconds or more to deliver. Running top rarely shows any resources being used:

top - 17:54:32 up 6 days, 21:37,  2 users,  load average: 0.00, 0.00, 0.00
Tasks: 123 total,   1 running, 122 sleeping,   0 stopped,   0 zombie
Cpu(s):  0.3%us,  0.0%sy,  0.0%ni, 99.5%id,  0.2%wa,  0.0%hi,  0.0%si,  0.0%st
Mem:   1916548k total,  1696236k used,   220312k free,   189352k buffers
Swap:        0k total,        0k used,        0k free,   386004k cached

free -m shows:

[gnet@itv ~]$ free -m
             total       used       free     shared    buffers     cached
Mem:          1871       1662        209          0        184        378
-/+ buffers/cache:       1099        772
Swap:            0          0          0

I cannot see anywhere where an issue could be found. I have checked /var/log/secure and /var/log/messages with no issues. I ran mysqlcheck on the DB and all tables report OK. Pinging the servers on the private network is as expected (quick). I see very few long queries in the MySQL query log.

My host (Rackspace) tells me there are no 'noisy neighbors' and that the parent node is fine, and there are no network issues.

What can I look at to see what the issue might be? I have run iotop and show only minor, quick writes. But when I'm ssh'd in, the connection "acts" like the server is under tremendous load.

Any ideas would be appreciated!

Answer 1

It seems the issue was, indeed, hardware. They migrated my VM to another host and the problem has disappeared.