[Samba] WinNT offline file attribut

[John E. Malmberg]

On Thu, 25 Apr 2002, Illtud Daniel wrote:
> "John E. Malmberg" wrote:
> 
> > Does Windows NT/2000 do any tests when serving shelved files, or does it
> > just assume that the client will do the right thing?
> 
> I have OTG's DX2000 HSM software running on NT. We can serve
> HSM'd directories with the normal windows sharing to PCs
> or SFM/MacServerIP for Mac clients. There are some issues
> with the Macs tending to want to access the icon information
> (thus fetching the files), but I'm fairly sure that the
> mac file sharing services certainly aren't aware of any offline
> attributes.

There are two ways to handle HSM, swap part of the file or swap all of the 
file.  If the HSM software leaves the part of the file most frequently 
accessed on the disk, then Windows clients may be able to access the 
portion of the file for it's icon and be happy.  This requires that the 
HSM software either statistically know what parts of the file are
frequently accessed or to make assumptions.  Eitehr way is overhead.

This would make Windows files happy.  I am not sure about the Mac's, as
they may expect a different file format, or the resource fork may be a
factor.
> 
> Really? I hope not! We've got ADIC engineers coming in on Monday
> to install AMASS (HSM on Solaris) on a Solaris 8 box here, and
> we've indicated to them that we'll be using samba and netatalk
> to serve the shelved directory to PCs & Macs, and they haven't
> objected. I'll call my ADIC tech contact and see if he can
> clarify.

How HSM's work is proprietary, and I have never been sucessful in getting
information as to their algorithms, but it appears that they leave only a
stub file on the real disk.  How much is left is the real question.

For the non-PC uses that I am familiar with, there does not seem to be
much reason to leave any part of the file on the disk once it is shelved.

So that means with out considering a product like SAMBA, a UNIX based HSM
program would not need to contain the algorithms to just swap part of a
file.

Also if the data that has been shelved has not been overwritten on the
disk, and the file is requested to be unshelved, I would expect that the
HSM software would know to just use the data.

The question that none of the Windows based HSM vendors would give me an
answer on was: Is there any way to make sure that a copy of all files
shelved and unshelved exists on the storage robot, and how do I restore
things when the real disk fails.  I would think that question should be
easy to answer.

It should be possible to get close to a current restore by putting in a
new disk, and letting the HSM restore the files as needed with a minimal
number of commands.

> I'll be trying samba (and netatalk) on a HSM'd volume on Monday, so
> I should be able to report back, if there's interest.

I am sure that there is interest.  Because of the caching issue, unless
you have enough files so that they all do not fit on the disk, you may not
notice a performance problem.

-John
wb8tyw at qsl.network
Personal Opinion Only