Hi,
For moderate amounts of data there is a safe, if dull, procedure,
providing only one site does it at a time.
1) Remove files with replicas elsewhere
2) replicate loners to local T1
3) repeat
The T1's would be expected to handle any SE-dcache/DPM-like move without
the need for moving the data off-site - as RAL did in fact.
There are surely more elegant solutions, and editing the sfns in the
database may even be practical with LFC, but this procedure should work
for current data volumes. This is certainly an argument for having the
sfns stored in a local catalog, which is the new Atlas DH model. In
addition the future system will treat local storage more like a temporary
scratch area, so we shouldn`t be in this situation again.
I`m happy to share my dodgy scripts, but the work must be done at least
at the T1 level in order to scale.
Cheers,
Rod.
On Tue, 20 Sep 2005, Burke, S (Stephen) wrote:
> LHC Computer Grid - Rollout
> > [mailto:[log in to unmask]] On Behalf Of Rod Walker
> said:
> > I don`t think anyone answered this. I thought the move from
> > classic SE to
> > DPM allowed the files to stay(unlike for dcache). I heard
> > this somewhere
> > but can`t find it written down now.
> > If the paths and hostname will stay the same, i.e. the sfn's are
> > unchanged, then you don`t need to do anything.
>
> The sfns might stay the same but the SURLs can't, at the least the
> scheme changes from sfn: to srm:. Also I think ownership and/or
> permissions have to change. There have been repeated requests from the
> UK for many months for a migration strategy, but as far as I know
> nothing has emerged so far.
>
> > If you have to move or
> > reregister data then RAL certainly have experience of doing this.
>
> I think RAL ran the old and new SEs in parallel for several months,
> which may well be the best way, but small sites don't necessarily have
> the resources to do it.
>
> Stephen
>
--
Rod Walker +1 6042913051
|