Data Compression Using mod_deflate

The mod_deflate module provides the DEFLATE output filter that allows output from your server to be compressed before being sent to the client over the network. Currently mod_deflate is using with newer version of Apache. mod_deflate is the replacement of mod_gzip which was used with older verion of Apache.

Enabling Compression

By default mod_deflate modules are enabled in Apache. To make sure check following line in Apache configuration file.

LoadModule deflate_module modules/mod_deflate.so

Enable mod_deflate by editing apache conf(vhost.conf) file for particular website,

<Directory "/path/">
       <IfModule mod_mime.c>
                AddType application/x-javascript .js
                AddType text/css .css
        </IfModule>
        <IfModule mod_deflate.c>
                AddOutputFilterByType DEFLATE text/css application/x-javascript text/x-component text/html text/plain text/xml application/javascript
        </IfModule>
        Header append Vary User-Agent env=!dont-vary
    </Directory>

OR

Enable mod_deflate by editing apache conf(httpd.conf) file,

Add the following lines to configure mod_deflate in your apache configuration file.

 <IfModule mod_deflate.c>
  # compress text, html, javascript, css, xml:
  AddOutputFilterByType DEFLATE text/plain
  AddOutputFilterByType DEFLATE text/html
  AddOutputFilterByType DEFLATE text/xml
  AddOutputFilterByType DEFLATE text/css
  AddOutputFilterByType DEFLATE application/xml
  AddOutputFilterByType DEFLATE application/xhtml+xml
  AddOutputFilterByType DEFLATE application/rss+xml
  AddOutputFilterByType DEFLATE application/javascript
  AddOutputFilterByType DEFLATE application/x-javascript
  AddOutputFilterByType DEFLATE image/x-icon
</IfModule>

To set the no-gzip note for a particular browser, so that no compression will be performed.

<Directory /var/www/html/>
    <IfModule mod_mime.c>
        AddType application/x-javascript .js
        AddType text/css .css
    </IfModule>
    <IfModule mod_deflate.c>
        AddOutputFilterByType DEFLATE text/css application/x-javascript text/x-component text/html text/plain text/xml application/javascript
        <IfModule mod_setenvif.c>
            BrowserMatch ^Mozilla/4 gzip-only-text/html
            BrowserMatch ^Mozilla/4\.0[678] no-gzip
            BrowserMatch \bMSIE !no-gzip !gzip-only-text/html
        </IfModule>
    </IfModule>
    Header append Vary User-Agent env=!dont-vary
</Directory>

Restart the apache service to complete the process

# service httpd restart

Testing Compression

After configuring compression in Apache we can see that content is being send by web server is compressed by mod_defalte by using below URL.
http://www.whatsmyip.org/http-compression-test/

Ref : http://tecadmin.net/how-to-enable-gzip-compression-on-apache/

Troubleshooting high loads on Linux servers

The load average represents the average number of processes that have to wait for CPU time during the last 1, 5 or 15 minutes.

What causes high server loads?

Excessive usage of any of the following items can typically cause this issue:

CPU
memory (including swap)
disk I/O

How can I check these items?

That depends whether you want to review their current resource usage, or historical resource usage.

Historical resource usage can be viewed using the "sar" utility.

The stats are collected when sysstat runs from cron (/etc/cron.d/sysstat). If crond is not running, sysstat will not be able to collect historical statistics.

or example, if you wanted to view the load averages for your server from the 28rd of the month:
sar -q -f /var/log/sa/sa28

the current day status: sar -q
Current CPU usage: top c
Historical CPU usage : sar -p
Current memory usage: free -m
Historical memory usage: sar -r  (%memused and %swpused), sar -s (%swpused)
Current disk I/O usage: iostat -x 1 10
Historial disk I/O usage : sar -d
process list: ps auxwwwf
system’s virtual memory statistics: vmstat 5 10 (10 times at 5 second intervals)

There are various actions you can take to find the cause of your high server loads. Here is a partial list that will always be incomplete:

Check the MySQL process list using "mysqladmin processlist" (or just "mysqladmin pr" for short)
Check the MySQL process list using mytop
tail your logs! Listening to what your server says is very important. Is your server being brute forced?
Run dmesg and check for possible hardware issues
Use netstat to view the connections to your server

Here are some logs to check:

syslogs: /var/log/messages, /var/log/secure
SMTP logs: /var/log/exim_mainlog, /var/log/exim_rejectlog, /var/log/exim_paniclog
POP3/IMAP logs: /var/log/maillog
Apache logs: /usr/local/apache/logs/access_log, /usr/local/apache/logs/error_log, /usr/local/apache/logs/suexec_log, /usr/local/apache/logs/suphp_log
Website logs: /usr/local/apache/domlogs/ (use this to find sites with traffic in the last 60 seconds: find -maxdepth 1 -type f -mmin -1 | egrep -v 'offset|_log$')
cron logs: /var/log/cron

Ref :
http://forums.cpanel.net/f5/troubleshooting-high-server-loads-linux-servers-319352.html
http://www.linuxjournal.com/magazine/hack-and-linux-troubleshooting-part-i-high-load?page=0,0