[Gnu-arch-users] Re: Why we might use subversion instead of arch.

[John Goerzen]

On 2004-02-26, Robin Farine <address@hidden> wrote:
> John Goerzen wrote:
>
>> Setting up a local revision library is out of the question due to the
>> apalling space requirements this would require.
>
> Well, today, a 200GB HD costs about 150 Euros and you a lot 
> of revisions can fit on such a beast. So is a revision 
> library really out of question?

Yes, for several reasons.  The machine in question is a 2U server with 5
SCSI disks in RAID-5.  Adding 200GB of storage to it is neither cheap
nor easy, and would mean downtime that is probably unacceptable.

Not to mention that 200GB is just a completely outlandish figure to ask
someone to have for this sort of project.

> I am using a greedy library. A 'tla changes' on a Linux 

What exactly is a "greedy library"?  I've seen terms like this floating
around but can't seem to find anything in the docs or help text about
it.

> 2.6.0 tree hard linked to the library and with a few changes 

Are you saying that you hard link the checked-out tree -- the thing you
obtain with "tla get" -- to the library?  That strikes me as very
dangerous and error-prone.

> in it takes about 3s (with name ids). On a tree two thirds 
> the size of the Linux kernel tree but with explicit ids, 
> 'tla changes' takes about 4s.

tla commit takes me on the order of minutes.  This on a dual 2GHz Xeon
machine with 15000RPM SCSI drives.

> So I am quite happy with tla but nevertheless admit that I 
> have no idea on how Subversion behaves with this same tree 
> in terms of storage requirements and operation time. Do you 
> have any concrete values?

Subversion takes up more space on-disk for this project than tla, but
behaves far quicker.  I may have posted about it at some point; I
originally tried this project with Subversion.  I seem to recall
Subversion using about twice the amount of space as tla for its
repository, though that advantage is probably being eaten up by the need
to cache so frequently with tla these days -- tla replay is really slow,
and tla update even more so.