I think using FD.sync() might have enabled the proper operation on
NFS in a much simpler way...
I argued quite a bit that the approach people were taking was
probably not correct, and/or a bug in NFS (which it seems there was
at least one that was corrected in a later release).
IMHO the work to make Lucene "work" on NFS was wasted - anyone using
NFS (and that knows the design of it) would say that it was against
the design.
They only needed to move Lucene into a "server" installation. Running
Lucene over NFS just isn't a good use of bandwidth or the architecture.
You ended up making Lucene way more complex for a very boundary
condition that had better solutions.
It is one of the reasons we have stuck with 1.9, and just merge
decently designed improvements.
On Nov 3, 2007, at 7:35 PM, Chris Hostetter wrote:
: This is simple not true. See FileDescriptor.sync().
:
: There are several options, but normally it is used so that when
close
: completes, all data must be on disk. This is a much slower way to
write data.
: It is very common in database systems when committing the log file.
Ok. I'll certainly take your word for it ... i've been trusting
the docs
for [File]OutputStream.flush()...
If the intended destination of this stream is an abstraction
provided
by the underlying operating system, for example a file, then
flushing
the stream guarantees only that bytes previously written to the
stream
are passed to the operating system for writing; it does not
guarantee
that they are actually written to a physical device such as a
disk drive.
I haven't looked at the internals of FileOutputStream or
FileDescriptor on
any particular platforms to see how exactly they work, but if
dealing with
the FD directly and using FD.sync() the magic bullet then I'd love
to see
a patch that uses it in FSDirectory.
I assume the SyncFailedException it throws is rare? If it is always
thrown when using things like NFS that may be a show stopper for using
sync() in Lucene ... many people have jumped through a lot of hoops
this
past year to get Lucene working on NFS; I'd hate to see all that
work go
out the window in an effort to make Lucene ACID. (I suspect there are
more users interested in using Lucene on NFS then on using it as a
transactional data store)
Throws:
SyncFailedException - Thrown when the buffers cannot be
flushed, or
because the system cannot guarantee that all the buffers have been
synchronized with physical media.
-Hoss
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