tar(I) always reads and writes disk files in 512 byte chunks

[Peter Gross]

Index:	/usr/src/bin/tar.c 4.2BSD

Description:
	4.2bsd tar seems patched together from the older v7 and 4.1
	versions.  The old versions did all their disk I/O using
	512 byte blocks..  On 4.2 this is suboptimal and makes tar
	much slower than need be.
Repeat-By:
	write a tar tape of large files
		or
	extract a tar tape containing large files
Fix:
	Should be made to use st.blksize to set optimal block size
	for disk read/writes.  Unfortunately this entails a lot of rewriting.

--peter gross
hao!pag