Dear Team,
One of our server got restarted suddenly and this is the log messages.

Mar 3 16:16:53 siu1 dhclient: DHCPREQUEST on usb0 to 169.254.95.118 port 67
Mar 3 16:16:53 siu1 dhclient: DHCPACK from 169.254.95.118
Mar 3 16:16:53 siu1 dhclient: bound to 169.254.95.120 -- renewal in 279 seconds.
Mar 3 16:17:54 siu1 shutdown[27781]: shutting down for system halt
Mar 3 16:17:58 siu1 pcscd: winscard.c:304:SCardConnect() Reader E-Gate 0 0 Not Found
Mar 3 16:17:59 siu1 smartd[3722]: smartd received signal 15: Terminated
Mar 3 16:17:59 siu1 smartd[3722]: smartd is exiting (exit status 0)
Mar 3 16:18:00 siu1 avahi-daemon[3660]: Got SIGTERM, quitting.
Mar 3 16:18:00 siu1 avahi-daemon[3660]: Leaving mDNS multicast group on interface usb0.IPv6 with address fe80::e41f:13ff:fe49:e4ef.
Mar 3 16:18:00 siu1 avahi-daemon[3660]: Leaving mDNS multicast group on interface usb0.IPv4 with address 169.254.95.120.
Mar 3 16:18:00 siu1 avahi-daemon[3660]: Leaving mDNS multicast group on interface eth0.IPv6 with address fe80::e61f:13ff:fe45:488.
Mar 3 16:18:00 siu1 avahi-daemon[3660]: Leaving mDNS multicast group on interface eth0.IPv4 with address 10.177.114.3.
Mar 3 16:18:03 siu1 xinetd[3536]: Exiting...
Mar 3 16:18:07 siu1 nm-system-settings: disconnected from the system bus, exiting.
Mar 3 16:18:07 siu1 hcid[3285]: Got disconnected from the system message bus
Mar 3 16:18:07 siu1 kernel: nm-system-setti[4045]: segfault at 0000000000000000 rip 0000000000000000 rsp 00007fffd4ab4798 error 14
Mar 3 16:18:07 siu1 rpc.statd[3231]: Caught signal 15, un-registering and exiting.
Mar 3 16:18:08 siu1 auditd[3130]: The audit daemon is exiting.
Mar 3 16:18:08 siu1 kernel: audit(1362307688.109:2005236): audit_pid=0 old=3130 by auid=4294967295
Mar 3 16:18:08 siu1 pcscd: pcscdaemon.c:572:signal_trap() Preparing for suicide
Mar 3 16:18:08 siu1 pcscd: hotplug_libusb.c:376:HPRescanUsbBus() Hotplug stopped
Mar 3 16:18:09 siu1 pcscd: readerfactory.c:1379:RFCleanupReaders() entering cleaning function
Mar 3 16:18:09 siu1 pcscd: pcscdaemon.c:532:at_exit() cleaning /var/run
Mar 3 16:18:09 siu1 kernel: Kernel logging (proc) stopped.
Mar 3 16:18:09 siu1 kernel: Kernel log daemon terminating.
Mar 3 16:18:10 siu1 exiting on signal 15
Mar 3 22:03:09 siu1 syslogd 1.4.1: restart.
Mar 3 22:03:09 siu1 kernel: klogd 1.4.1, log source = /proc/kmsg started.
Mar 3 22:03:09 siu1 kernel: Linux version 2.6.18-164.el5 (mockbuild@x86-003.build.bos.redhat.com) (gcc version 4.1.2 20080704 (Red Hat 4.1.2-46)) #1 SMP Tue
Aug 18 15:51:48 EDT 2009
Mar 3 22:03:09 siu1 kernel: Command line: ro root=LABEL=/1 rhgb quiet
Mar 3 22:03:09 siu1 kernel: BIOS-provided physical RAM map:
Mar 3 22:03:09 siu1 kernel: BIOS-e820: 0000000000010000 - 000000000009c400 (usable)
Mar 3 22:03:09 siu1 kernel: BIOS-e820: 000000000009c400 - 00000000000a0000 (reserved)
Mar 3 22:03:09 siu1 kernel: BIOS-e820: 00000000000e0000 - 0000000000100000 (reserved)
Mar 3 22:03:09 siu1 kernel: BIOS-e820: 0000000000100000 - 000000007aee7000 (usable)
Mar 3 22:03:09 siu1 kernel: BIOS-e820: 000000007aee7000 - 000000007cfbb000 (reserved)
Mar 3 22:03:09 siu1 kernel: BIOS-e820: 000000007cfbb000 - 000000007d861000 (usable)

so anyone please help me ...

Which distro? and what does dmesg says:

Restarted successfully? or giving error?
Do you want to know, why was it restarted, correct?

Yes, its started successfully, now its working fine but i want to know why it was restarted.

according to the timestamps it has been halted

I hope this is HDD issue in this server we have RAID 1 configuration, how will know which hard disk having issue..

Regards
Abdul

Can you provide output of this:

The same way you know about ANY failing hardware...by looking in the system logs.

And as others have said..your server was halted. That means, someone shut it down, either by typing in "shutdown -h 0", via SNMP, or "init 0". Find out who did it. Ask your co-workers, or look in the .bash_history files of the people involved (and the sudo logs), to see who issued the command.