[CentOS] Understanding iostat

We have a load balancer/session server that manages sessions in small 
files. I did a grep on the directory of session files and the server 
load went from 0.50 to 10.x, for all intents and purposes we were down 
until I canceled the grep.

According to this article on 
http://www.thattommyhall.com/2011/02/18/iops-linux-iostat/ tps is 
roughly analogous to iops. Running iostat on the device reports a tps 
that sometimes hits as high as 2000. Given a fairly standard 7200 RPM 
SATA drive, with potential IOPS as high as perhaps 100, how is this even 
remotely possible? Is it due to sequential writes?

Thanks,

Ben