High Disk write and space taken by PostgreSQL

Hi,

My application has high data intensive operations (high number of inserts
1500 per sec.). I switched my application from MySQL to PostgreSQL. When I
take performance comparison report between mysql and pgsql, I found that,
there are huge difference in disk writes and disk space taken. Below stats
shows the difference between MySQL and PostgreSQL.

*MySQL**PostgreSQL*Inserts Per Second*15001500Updates Per Second*6.56.5Disk
Write Per Second*0.9 MB6.2 MBDatabase Size Increased Per day*13 GB36 GB
* approx values

Why this huge difference in disk writes and disk space utilization? How can
I reduce the disk write and space ? Kindly help me. Please let me know, if
you require any other information(such as postgres.conf).

Thanks,
Ramesh