Ext3 can support files up to 1TB. With a 2.4 kernel the filesystem size is limited by the maximal block device size, which is 2TB. In 2.6 the maximum (32-bit CPU) limit is of block devices is 16TB, but ext3 supports only up to 4TB.

Actually as of 2.6.18 (or is it .19.*), ext3 kernel code should support the full 16T, at least in terms of being able to address that many blocks w/o corruption. Eric Sandeen did a fair amount of work in that time frame to root out all the sign overflows etc to allow ext3 to get to 16T.

From: Linux ext3 FAQ