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[Patrick Phalen]

[Pavlos Christoforou, on Fri, 10 Mar 2000]

:: Hi Patrick -
:: 
:: What happens if one manually deletes a file that is part of a transaction
:: involving many objects/files? How would transaction boundaries be enforced
:: on a filesystem? I am interested in hearing your thoughts on the issue
:: since it seems you have already done some work on it.

I have done nothing on this, unless you count daydreaming. ;>) At one
point, I had idly asked if anyone thought this might work, expecting
that some knowledgeable soul would immediately shoot the idea down.
Surprisingly, both Jim Fulton and Hans Reiser seemed to see that it was
in the realm of possibility, but not easy.

Of course, you have identified the hard part. Back in December, Jim
Fulton had the following reaction (below). Afterward, someone else at DC
told me that when Jim says it "getting transactional semantics right
might be a tad tricky" he means your head will explode. :)

Still ... since Linus Thorvalds has refused to add the complexity of
journalling to the Linux buffer cache, the people hacking on reiserfs
and other journalling filesystems, have been forced to implement their
own mechanisms for keeping track of dirty data. So one wonders if these
might be adaptable in some fashion, much as they are used to support
high availability network filesystems like Intermezzo, which exploits an
existing filesystem as a cache and wraps around it.

So, in answer to your question, I have no idea. ;)

===========

[Jim Fulton]
Would you imagine using the reiserfs as a ZODB storage?
If one was going to use a file system as an object store, 
then the reiserfs would be attractive due to it's effective
support for small files. Is this what you had in mind?

The ZODB has a well-defined "storage interface" that should
make implementation of a reiserfs- (or just an fs-) 
based storage reasonably straightforward, although getting
transactional sematics right might be a tad tricky.

Jim


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