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From "C. Michael Pilato" <cmpil...@collab.net>
Subject Re: svn 1.8 migration - directory deltification and revprop packing
Date Tue, 11 Jun 2013 12:52:48 GMT
One advantage of being in a room full of Subversion developers, specifically
the guy that implemented all this stuff, is that I can ask him directly
about how to respond to this mail.  :-)  Hopefully I will accurately
represent the answers Stefan Fuhrmann just gave me to your questions.

On 06/10/2013 03:05 PM, Thomas Harold wrote:
> a) Why are directory/property deltifications turned off by default?

Stefan's jovial first answer was, "Because I'm a chicken."  :-)

Fortunately, he didn't stop there.  He explained that there is no known
correctness risk -- you're not going to damage your repositories by enabling
the feature.  But he wanted to phase in the feature to allow time to collect
real-world data about the amount of space savings folks are actually
observing in their repositories.  The feature is on by default in his
proposed next version of the FSFS format.

> b) Is there a global setting file that can be used to enable
> directory/property deltifications? Or will we have to update the fsfs.conf
> file for each newly created repository in order to get this feature?

In 1.8, you'll need to toggle this for each new repository manually.

> c) Is it a safe assumption that in order to apply this change to an older
> repository that we will need a dump/load cycle?  Will we need a full dump or
> will an delta style dump suffice (--deltas option of svnadmin dump command)?

Not exactly.  You can apply the change to an older repository sitting behind
a server still running 1.8, and any new directory/property lists will be
stored in a deltified fashion.  If you want retroactive deltification of
existing data, then yes, you'll need to dump and load your repositories.
But as explained in the release notes, you can dump and re-load right back
into a previous version of the repository format if you'd prefer to maintain
compatibility with older server versions.

As for the --deltas option, that has nothing in the world to do with the
types of deltas we're discussing here.  (As an aside, I would highly
recommend that, unless you need your dumpfiles to be smaller, avoid the
--deltas option.  The performance penalty of using it isn't worth it.)

> #2 - revision property (revprops) files packing
> 
> a) Will there be a "svnadmin pack" command like there was for SVN 1.6? Or
> will we need to do a full dump/load of the repository to pack the revprops?

The existing 'svnadmin pack' command will govern both revision and revprop
packing, and will keep the two in sync with each other.  'svnadmin upgrade'
will also take the opportunity to synchronize the packing status of the
revision properties with that of the revision backing files.

> b) Does revprop caching only need to be enabled for http/https access and
> does it have any effect on svn+ssh access?  (All of our users currently use
> svn+ssh access, but we are considering moving to http/https.)

Each server has its own cache enable/disable configuration mechanisms, and
both benefit from the revprop caching being enabled.

-- 
C. Michael Pilato <cmpilato@collab.net>
CollabNet   <>   www.collab.net   <>   Enterprise Cloud Development


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