Re: WC permissions

Ryan Hunt wrote:

> As far as I was aware the only issue with mounted file systems was with the
> repository, not the WC. If this is not the case can you identify the issues
> that will arise due to accessing a WC across a network file system?

Apart from the bandwidth required to transfer enormous files over a LAN link,
both SVN and CVS are written to assume that the WC is under the exclusive
control of one process. I don't know exactly what would be the worst case, but
I could see one user in the middle of a large update while another begins a
commit as being a problem. I don't want to spread FUD without cause, but I'm
pretty confident that shared WC's are a bad idea.

>
>> Secondly, I would seriously doubt that subversion will scale to 5TB WC's
>> (not to mention what this means the repository must look like).
>>
>
> As far as I was aware the only limitations in this capacity were those due to
> the berkeley bd.

There is also the issue that if the individual files are very large, the time to
produce the version delta may be so large that the system would have difficulty
keeping up (depending on the speed of the changes). Scaling has a lot more to
do with the whole process, not just the storage.

>> Unless the differences between versions are themselves significant (as
>> opposed to just being able to extract any given version),
>
>
> Is there any significant difference?
>

Yes. If you only need to retrieve an arbitrary version of a file, you can just
as easily copy the file off to another location (c.f. snapshots below). With
source-code (i.e. non-binary), frequently the diff between versions is itself of
some important (i.e. what code changed).

> I am not terribly familiar with SANs and the snapshot feature. Do you have
> any good links that describe this process?

They are just automatic backups to a protected portion of the volume. Snapshots
are available from several NAS vendors (NetworkAppliance for example has hourly
snapshots available). They require 100% additional storage per file per
snapshot (but drives are cheap these days). Here's something from NetApps website:

        http://www.netapp.com/tech_library/3002.html

(not a recommendation for their product, just I know they have them).

HTH

John

-- 
John Peacock
Director of Information Research and Technology
Rowman & Littlefield Publishing Group
4501 Forbes Boulevard
Suite H
Lanham, MD  20706
301-459-3366 x.5010
fax 301-429-5748
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