Backup Size

[Jay Hall]

I am sure there is an easy explanation for this, but I cannot find it.

I am backing up my /etc directory using the following command.

tar -cvf - /etc | dd of=/dev/nsa1 obs=10240

When the command completes, I receive the following message.

3080+0 records in
154+0 records out
1576960 bytes transferred in 0.179921 secs (8764740 bytes/sec)

What concerns me is when running du -h /etc, the size of the folder is  
reported as 1.7M.

Is the number of bytes written to the tape less than the reported size  
of the directory because of the way the files are written to the  
tape?  If so, how can the amount of space used be calculated?

Thanks for your help.


Jay