temporary table size

Hi, now I am using Linux Red Hat 6.2J, and the disk is being storage raid
0(stripe set)
4GbyteX4=16. I installed PostgreSql7.02 into this machine, and
as making database, there is several error messages.
First of all, I create table, and whether it is because disk raid,
or postgress, error message came out.
========================================================
#created table time_sum_200006
#and carried out
INSERT into time_sum_200006
(Select time,
SUM(visit),
SUM(bytes)
from logdb_200006
group by time);

ERROR: ltsReadBlock: failed to read block 16672 of temporary file

ERROR: cannot read block 41419 of logdb_200006(second trial)
======================================================
Maybe this happened because lack of disk space, for temporary table
may be too small to put datas.
Is it possible to disperse size of temporary table, just as oracle's alter
table space?
Or is there another way to user disk raid, and if not raid, how can sum up
the size?

best regards,

Makiko Kudo