High Load on ZCS (Open Source) 7.1.0

[mutface]

Version : 7.1.0_GA_3140.RHEL5_64
O/S : CentOS release 5.6 (X86_64)
RAM : 8Gb

Problem:-
zimbra 8558 93.9 3.3 719080 276548 ? Sl May09 19294:25 /opt/zimbra/java/bin/java-XX:ErrorFile=/opt/zimbra/log-client-Xmx256m-Dzimbra.home=/opt/zimbra-Djava.library.path=/opt/zimbra/lib-Djava.ext.dirs=/opt/zimbra/java/jre/lib/ext:/opt/zimbra/lib/jars:/opt/zimbra/lib/ext-common:/opt/zimbra/lib/ext/clamscanner-Dpython.cachedir=/opt/zimbra/data/tmp/jython-cachedirorg.python.util.jython/opt/zimbra/libexec/zmconfigd

Mount Information (we mounted a RAM drive for the tmp directory to make amavisd faster)

[root@mx etc]# mount
/dev/sda2 on / type ext3 (rw)
proc on /proc type proc (rw)
sysfs on /sys type sysfs (rw)
devpts on /dev/pts type devpts (rw,gid=5,mode=620)
/dev/sda6 on /opt type ext3 (rw)
/dev/sda5 on /tmp type ext3 (rw)
/dev/sda1 on /boot type ext2 (rw)
/dev/shm on /opt/zimbra/data/amavisd/tmp type tmpfs (rw,noexec,nosuid,nodev,size=768m,mode=750,uid=500 ,gid=500)
none on /proc/sys/fs/binfmt_misc type binfmt_misc (rw)
sunrpc on /var/lib/nfs/rpc_pipefs type rpc_pipefs (rw)

[zimbra@mx etc]$ zmcontrol status
Host mx.<<host name>>
antispam Running
antivirus Running
ldap Running
logger Running
mailbox Running
mta Running
snmp Running
spell Running
stats Running
zmconfigd Running

I have searched on the forum + Google and cannot find any similar posts for the same issue. Please delete this post if it has been reported already - especially for Zimbra 7.1.0. (Open source version).

If anyone has any ideas - please let us know. Many thanks.