[virt-tools-list] [PATCH libosinfo 1/3] Fill out media for all Ubuntu distros

[Christophe Fergeau]

On Thu, Feb 23, 2012 at 01:44:35AM +0200, Zeeshan Ali (Khattak) wrote:
> On Thu, Feb 23, 2012 at 1:25 AM, Daniel P. Berrange <berrange at redhat.com> wrote:
> > Yep, the name is about the only difference between them - all the ISO
> > metadata is identical. The other thing I considered is to add an MD5
> > checksum of the ISO file, which would trivially distinguish them,
> > but I fear that would make it too unique.
> 
> That might be a very good idea actually (Christophe was meaning to do
> that any ways?) but calculation of md5 takes a very long time:

I wondered out loud if it would be a good idea to have that in the
database, that's it :)

> so I'll recommend to restrict it to first N bytes, where we could
> think/discuss the value of N but 1MiB should be good enough and takes
> very little time:

Yup, this is what I was thinking too before reading your email.

> $ time dd if=~/ISOs/Fedora-16-x86_64-DVD.iso bs=1M count=1 2> /dev/null |md5sum
> e25ea147176f24239d38a46f501bd25e  -
> 
> real	0m0.011s
> user	0m0.004s
> sys	0m0.008s
> 
> Actually if we start using md5sum for detection, we can pretty much
> remove all other detection logic/extraction.

Depends, the other logic will be much faster if for some reason we end up
trying to identify remote medias over a slow link.

Christophe
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 198 bytes
Desc: not available
URL: <http://listman.redhat.com/archives/virt-tools-list/attachments/20120223/cba1f44d/attachment.sig>