[Samba] Accessing files though samba and efficient copy

[Norbert Hanke]

Robocopy would do that on Windows...

Could using rsync with a CIFS-mounted shared directory achieve the same?
I don't know how well it performs though, but at least figuring out
which files _not_ to copy could be fast. Just and idea...

Btw, good idea to use changing DFS / reparse points to change content :)

regards,
Norbert

On 17.12.2023 19:33, Michael Tokarev via samba wrote:
> A while back I tried to come with a solution to a problem - updating
> an application
> (consisting of a large number of files) which is accessed though a
> samba server.
>
> The problem was that when updating a file which is open / in use in
> windows,
> Bad Things (tm) happen.  Unix allows such update "behind windows's
> back", and
> when windows tries to open this file again, it discovers this is a
> different
> file already, and fails badly.
>
> The solution to this was to use samba to update files too, - and sure
> thing,
> this way we immediately know if a file is in use, - because the update
> just
> fails without a way around it.
>
> So there are 2 bad cases and no good: either windows fails to open
> updated
> files, or there's no way to update at all.  So far so good.
>
> I worked around this in a different way: by creating a reparse point
> for the
> whole application directory (msdfs root = true) and in case we have to
> update
> a file which is in use, we just create a "new version" of the whole thing
> and update the referral, so with time all clients switches to the new
> version.
>
> Now the next question is: how to copy files effectively?  We always used
> rsync for the copy, running on the samba server.  It's fast to check a
> few
> 1000s of unchanged files and sync just the ones which changed, just
> the actual
> differences.  But if we do it though samba in order to determine if
> any of
> the new files has changed, we have to copy using regular windows copy
> mechanism,
> which is insanely slow in our case (since files are large).
>
> It seems to be a never-ending story...
>
> /mjt
>