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Re: The default FS type

From: <kfogel_at_collab.net>
Date: 2005-04-06 18:38:08 CEST

Greg Hudson <ghudson@MIT.EDU> writes:
> In IRC, we have a little disagreement over how the default FS type
> should be determined in 1.2. Here are our options:
>
> (1) Trunk status quo: The default is FSFS. If svn is built with
> --enable-dso and FSFS is not installed, "svnadmin create" will
> fail unless --fs-type=bdb is specified.
>
> (2) No default. You must specify an FS type when creating a
> repository.
>
> (3) The default is determined at runtime; FSFS is preferred, but if
> svn is built with --enable-dso and FSFS is not installed, BDB is
> the default. (This is similar to how 1.1 determines the
> default, with the preference switched from BDB to FSFS.
> Although 1.1 makes the decision depending on whether BDB was
> built, not whether it is installed.) Documentation needs to be
> careful not to write in stone what the default is.

-0.9 on (2). I think it would be very bad not to have a default. Why
make people's lives harder? Because they should be forced to make a
conscious decision? Bah humbug. Let them decide whether or not they
need to make a decision. Things should work out of the box as much as
possible.

For this same reason, I prefer (3) and (1) in that order.

> Since we always build FSFS, there is some disagreement about whether
> it should always be installed. I think FSFS should be considered part
> of the Subversion core (a "mandatory to implement" mechanism, in IETF
> terminology), since it has no dependencies; breser believes that it's
> important to be able to not install mechanisms which one doesn't plan
> to use.

I agree with you, that it should be installed. Which makes (1) that
much more attractive, since the failout option could happen only
rarely (the admin would have had to do something special to end up not
installing fsfs).

By the way, libsvn_fs_fs takes up only 1 meg on my Debian GNU/Linux
system. Size wasn't really Ben Reser's issue anyway, it's more
cleanliness and security for him, but it's worth pointing that we're
not talking about a huge library here.

> Here are the preferences from IRC:
>
> ghudson: (1) (3 better than 2, if it comes to that)
> cmpilato: (1) or (2)
> breser: (2) or (3)
> kfogel: (1) or (3)
> dlr: (1) (assuming the failure is graceful)
> fitz: (1)
>
> No one brought up the idea of a veto on any of the options, so we can
> go by the majority preference. The IRC poll suggests (1) is the most
> popular; this is your chance to speak up if you're not represented
> there.
>
> (The astute reader may note that I didn't object to r10299, which made
> FSFS the default back end in 1.1 if BDB is not built. I did feel kind
> of ooky about that at the time, but couldn't articulate my reasons.
> Now I know: in my opinion, the overriding concern here is our ability
> to confidently document what the default is. If you really don't want
> to install libsvn_fs_fsfs, that's okay, but having "svnadmin create"
> fail by default in that scenario is the right answer.)

I can see that argument; and anyway am happy enough with (1).

-Karl

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Received on Wed Apr 6 22:11:15 2005

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