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From Mark Miller <markrmil...@gmail.com>
Subject Re: [jira] Resolved: (LUCENE-1044) Behavior on hard power shutdown
Date Sun, 04 Nov 2007 00:40:50 GMT
I think it would be great if it where an option. Perhaps even a sandbox 
implementation that could wrap or replace a few classes. Maybe that 
complicates things too much, but that way you could just not use the 
transaction system if you where on NFS (if that ends up being a problem) 
or you didn't want to pay a performance cost.

Maybe a Derby guy would pitch in.

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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>   

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