[mbackup-devel] xml as a tape header: the cons

[James O'K. <jo...@mi...>]

The only thing I have against using xml as a tape format is the extra tape
space that it would use. I wrote this quick example:

<?xml version="1.0" ?>
<mbackup:header>
<mbackup:date>966968837</mbackup:date>
<mbackup:filename>/usr/local/bin/foobar</mbackup:filename>
<mbackup:hostname>uhura.midnightlinux.com</mbackup:hostname>
</mbackup:header>

I'm not sure if that's true valid xml, but I think it's close enough for
this example. I also have this more traditional header format:

96696883724uhura.midnightlinux.com21usr/local/bin/foobar

9 digit time, 2 digit next field length, hostname, 2 digit next field
length, filename.

Both give the same information. The xml one is 215 bytes and the other one
is 58 bytes.

I also gathered some data that is typical of the data we use at work:

[root@cadillac round5]# du -a|wc -l
 306050
[root@cadillac round5]# du -s 
4070060 .

306,050 files using about 4 gigs of space. 
With the xml header, there is 65M of header data to label 4gig of data.
With the other header, there is 17M of header data to label 4gig of data.

Given this is a simple header and doesn't have all the data a full header
might have, but I feel that the xml header will grow faster than the other
header, even if we don't use the mbackup namespace part.

Just something to consider...

-james