Thoughts on Chapter 5

Brian W. Fitzpatrick fitz at
Sat Feb 24 15:19:56 CST 2007

OK.  This chapter covers a *ton* of data about an arcane subject and
it's a nice fluid read, but reading the chapter end-to-end, I felt
like I had to wade through a *ton* of BDB minutiae that 99% of the
repository admins won't ever have to deal with.  I don't have a
solution in mind for this, but I found it to be distracting and wonder
if we can't better title sections that are BDB specific so that FSFS
admins don't have to read all the way through just to find out that it
doesn't apply to them.

You may need to take some of these comments with a grain of salt as I
personally don't recommend that people use bdb at all.  Aren't we
going to prescribe one over the other?

"Planning Your Repository Organization":
- one other reason to have separate repositories is when you have
completely different types of data in each project: eg, one project
has source code, and another has 100MB Photoshop files in it.

- The last example of repository organization is one that I've rarely
seen used.  Shouldn't we recommend that most folks use the 1st example
for multiple projects in a single repo (i.e., I'm not seeing a lot of
"prescription" here, but mostly "description"

"Choosing a Data Store":

In the table:
- "Scalability: repository size": I don't understand what this
means--does this mean that fsfs repositories take up less space on
disk or that you can't use it for repositories with tons of data (and
if it's the latter, I think it's incorrect--Apache uses fsfs).

- "Performance: Isn't BDB < 10% faster than FSFS in checking out the
latest revision?  I thought ghudson mailed stats on this to the list
that showed it's a negligible difference.

-We should note that BDB has an extra dependency: BDB itself

- Also, doesn't FSFS deal better with mixed repository access
mechanisms (http:// + svn://)?  Should we mention this?

- Footnote starting "Berkely DB requires": Maybe mention that *no*
remote filesystem implementation currently does this right?

- BDB & FSFS subsections: Maybe these could be divided into a
"summary" and "gritty details" part?  I really doubt that most admins
give a hoot that BDB directory mods are O(n^2) and FSFS's are O(n).

- FSFS subsection:  fsfs really isn't "immature" any more, and it's
been stress tested a lot.  I'd say that this paragraph is mostly FUD
and should go.

"Creating the Repository"
- Maybe move the 1st tip up a little bit?
- Make the Warning more threatening?  We had some dude on the #svn
channel talking about how he edited one of his rev files (I am *not*

- 1st footnote:  I used to agree that the inability to obliterate a
rev is a feature, but after talking to dozens of people in various
roles (open source, closed source, including the BSD dudes), I now
think that it *is* a missing feature.  FreeBSD *can't* have to do
something that would require thousands of people to recheckout huge
working copies (eg the ports tree).

"removing dead transaction"
- Isn't this BDB only?  I thought these were no-ops in fsfs...

"repository recovery":
- This should be specified as BDB specific in the title

"repository replication":
- The 'svn>' prompt confused me--I thought it was some sort of weird
svn shell at first.

- using the username 'syncprop' in your examples is extremely
confusing--reminds me of properties.  Can't we use harry or sally?



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