On Thu, 6 Jul 2006 12:02:48 +0100
brian davies <[log in to unmask]> wrote:
> How can you sync an srm contents with a grid file catalog? A file in a
> SRM could be in any file catalog around the world? unless you have a
> list of all catalogs that an experiment has around the world, how can
> you tell if the reason that a file is not in a catalog is because of a
> sync problem or just that you are looking at an incorrect catlaog?
> Brian
That is a reason why the SRM should support, returning errors for files
not found as they are currently off line, and higher level tools should
do the job of syncing databases, probably the tools should be bound one
to one with a catalogue.
Regards
Owen
> On 06/07/06, Kostas Georgiou <[log in to unmask]> wrote:
> > On Thu, Jul 06, 2006 at 11:24:09AM +0100, Owen Synge wrote:
> >
> > > On Thu, 6 Jul 2006 09:32:51 +0100
> > > Greig A Cowan <[log in to unmask]> wrote:
> > >
> > > > Hi Andrew,
> > > >
> > > > > Does dCache's SRM check that the box hosting the pool is
> > > > > online when the SRM answers a query about one of its files? ie
> > > > > is the issue about not using resilient dCache just that a
> > > > > box/pool could go offline, or that plus the danger that the
> > > > > SRM will be falsely claiming to have files that are now
> > > > > offline?
> > > >
> > > > Like Derek has said already, if dCache can't get a file from an
> > > > online
> > > >
> > > > pool, it expects to be able to get it from tape or for an
> > > > offline pool
> > > >
> > > > to become available again.
> > >
> > > This is in my understanding also, I personally don't like the NFS
> > > model of blocking and locking the file system until it comes on
> > > line again. I prefer the idea of failing with an error quickly.
> > > The problem is the streaming POSIX model does not have space for
> > > presenting a currently unavailable file system that may come back
> > > and POSIX is a widely used standard. Because of this code
> > > developed against POSIX IO does not have checks for media changing
> > > to off line. SRM's though don't have such history and share nearly
> > > no state between client and server so could fail rather than
> > > block.
> > >
> > > I have to support the (gsi)pnfs, (I assume rfio also) POSIX layer
> > > blocking as they need to map to current expectations for a POSIX
> > > layer and behave in the same way as NFS.
> >
> > POSIX does not require you to block, nfs for example (not that it's
> > posix compliant) has the soft mount option that will give you an I/O
> > error in case of a timeout. You can (if it's sensible to do so is
> > another matter) just send an I/O error (return EIO) if the file
> > somehow disappears (because the pool is down or whatever).
> >
> > Kostas
> >
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