partitioning os swap data log tempdb

Hi,

we want to migrate from MS SQL Server (windows2000)
to PostgreSQL (Linux) :-))
and we want to use the old MSSQL Hardware.

Dual Pentium III 800
1 GB RAM
2 IDE 10 GB
2 RAID Controller (RAID 0,1 aviable) with 2 9GB SCSI HDD
1 RAID Controller (RAID 0,1,5 aviable) with 3 18GB SCSI HDD

The configuration for MS-SQL was this:
OS on the 2 IDE Harddisks with Software-RAID1
SQL-Data on RAID-Controller with RAID-5 (3 x 18GB SCSI Harddisks)
SQL-TempDB on RAID-Controller with RAID-1 (2 x 9GB SCSI Harddisk)
SQL-TransactionLog on RAID-Controller with RAID-1 (2 x 9GB SCSI Harddisk)

Can i make a similar configuration with PostgreSQL?
Or what is the prefered fragmentation for
operatingsystem, swap-partition, data, indexes, tempdb and transactionlog?

What is pg_xlog and how important is it?

What ist the prefered filesystem (ext2, ext3 or raiserfs)?

We want to use about 20 databases with varios size from 5 MB to 500MB per
database
and more selects than inserts (insert/select ratio about 1/10) for fast
webaccess.

Thank you for your hints!

Bye,
Mario