Looks like we have been chasing similar issues. (I am trying to
get several MySQL servers in a a system that has some similarities with
yours, albeit in a different environment. The system has several processors
that can see a shared disk, but also shared memory (in addition to local
The symptoms that you describe appear to stem from caching.
I am studying the source at this moment, and would like to point you to
functions like flush_io_cache and flush_key_blocks. Perhaps you
could change the code to invoke those functions at the end of each
query before you release the file locks to make sure all changes are
By the way, did you only change the fcntl calls in sql/locks.cc ?
I am under the impression that one would have to change the locks in
>From: Denis Pithon <denis.pithon@stripped>
>Subject: MySQL parallel server [long mail]
>Date: Fri, 26 Jan 2001 21:51:26 +0100
>Yes, it's again a mail about MySQL parallel server and this one is
>quite long... I work for two months to enable MySQL as a parallel
>server on Linux cluster. As you can guess, I encountered a bunch of
>** Context **
>At Lineo HA, we provide a Linux based software (Availix) which powers
>a CompactPCI hardware. Roughly, this hardware features one disk,
>shared between a couple of active nodes (up to 5). Each node could be
>seen as a diskless Linux PC, and all nodes runs the same service (one
>of httpd, ftpd... or why not... mysqld). IPVS runs on a particular
>node (controller) and dispatch IP query to the others. I hope that you
>understand that for a such hardware solution, replication is
>unfortunately not suitable.
>... deleted .....
>I have to explore the source deeper. I have seen many IO caches (bad
>news for me) and even a mmap (sql_mmap.cc), ouch! To check if we could
>use MySQL as a database parallel server I wan't to cancel the use of
>the cache. Is it possible ? And is it really usefull ?
>OK, I hope I hurt nobody in the MySQL development team! I know that
>I'm trying to slow down a formula 1 to a snail speed :-) But the
>results I have with MySQL are terrifically better than these of mSQL,
>PostreSQL and actual commercial products (DB2, Informix, Sybase...)
>wich are designed for distributed database only.
>Thanks a lot for your attention !
>Denis Pithon phone +33 (0) 1 41 40 02 13
>Software Engineer fax +33 (0) 1 41 40 02 01
>Lineo High Availability Group mail denis.pithon@stripped
>Before posting, please check:
> http://www.mysql.com/manual.php (the manual)
> http://lists.mysql.com/ (the list archive)
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