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From Daniel Noll <dan...@nuix.com>
Subject Re: Client/server plus network storage of database files
Date Thu, 25 Sep 2008 23:59:58 GMT
Valentin Cozma wrote:
> Stanley Bradbury wrote:
>> Not being a hardware or network guy I  can't speak in detail to all 
>> the TLAs you are using but do know the following is documented:  Derby 
>> database files must reside local to the machine hosting the Derby DBMS 
>> engine.  So that leaves out anything over TCP/IP and I know that NFS 
>> mounts, Windows file shares and Samba mounts.  These systems will 
>> result in corruptions because there is not way to insure that a 
>> physical write to disk was completed.
> 
> from what I know the problem is that nfs blocks and doesn't raise an 
> exception until SO tcp timeout is reached ( linux default 2 hours )
> 
> don't know about samba

With CIFS/SMB you issue SMB_COM_FLUSH to flush, and it's documented as 
flushing to disk -- Samba can honor this (but the setting defaults to 
off).  Also, what you describe is NFS2 -- NFS3 can work asynchronously 
if you want, but it can still operate in NFS2 mode as well.

So really, CIFS and NFS both appear to be okay for syncing -- NFS is 
trickier to get working properly for locking, but that's another issue.

In any case, in my case the database has not been corrupted -- the 
network went down, came back up, and Derby *thought* the database was 
corrupted, but on forcing a shutdown and opening it again it worked.

So my original question stands but I'll rephrase it -- in this 
situation, is there some way Derby can do this reconnection itself at 
the store level, or is there some way it can do it at the Network Server 
level, or do we have to shut down the entire Network Server and all its 
embedded databases to do it at our own level?

Daniel


-- 
Daniel Noll                            Forensic and eDiscovery Software
Senior Developer                              The world's most advanced
Nuix                                                email data analysis
http://nuix.com/                                and eDiscovery software

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