lastlog file size is HUGE..!!

Dear All,

In one of my server running on RHEL5.10 32-Bit Arch the lastlog size too big.
Which is causing a CPU spike when I try to copy/backup the file.

The server goes hung. Can someone help on fixing this.
When Backup is initiated the server goes HUNG due to out of CPU...!!!!

[root@test log]# du -sh lastlog
184K lastlog
[root@test log]# du -sb lastlog
292088859104 lastlog
[root@test log]#

[root@test ~]# vgs
VG #PV #LV #SN Attr VSize VFree
VolGroup00 1 5 0 wz--n- 278.34G 191.44G
[root@test ~]# ls -lh /var/log/lastlog
-rw-r--r-- 1 root root 273G Apr 16 11:43 /var/log/lastlog
[root@test ~]#