f20 - yum locally rebuilding deltas is so slow

[Chris Murphy]

On Dec 19, 2013, at 3:42 PM, T.C. Hollingsworth <tchollingsworth at gmail.com> wrote:

> On Thu, Dec 19, 2013 at 3:30 PM, Robert Moskowitz <rgm at htt-consult.com> wrote:
>> I just started a yum update fire* libre* that took next ot no time to
>> download from my local repo, but took over 10 min to build the local delta.
>> Seems I am better of NOT having drpms available.
> 
> Yeah, if you have a local mirror there's no point in using delta RPMs
> (or mirroring them, you could happily exclude them from your rsync if
> you wanted).  You don't need to save bandwidth over your LAN, do you?

Does anyone know exactly what's happening during the rebuild? I understand from light documentation how deltarpm works, what I'm not sure is if most of the time is spent reconstructing a virtual oldrpm from an installed rpm, or applying the delta, or writing out the new install? 

If it's not the former reconstruction aspect, it seems like a Btrfs aware deltarpm could simply write out the delta blocks to disk, which would be rather small, and then obsolete the old ones if the operation is successful. Fully rewriting the files isn't necessary by design with Btrfs.

Chris Murphy