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Re: MySQL + NAS(NFS) - Possible solution?
Posted by: Ingo Strüwing
Date: September 26, 2005 05:09AM

Difficult to say. I never did anything with O_DIRECT. But since the description seems to say that the application has to wait until the data are on disk, I don't believe that this would make things much faster.

OTOH, I experienced quite often that I was wrong with such beliefs.

What seems to be quite clear: This option must be disastrous for MyISAM performance. MyISAM writes every row (!) to the file system cache. With O_DIRECT it would have to wait for every row to travel the network and settle on disk.

InnoDB should only write in pages, when they are evicted from its cache or at savepoints. And in most cases InnoDB should need to know that the stuff is on disk. So O_DIRECT makes sense here. (Still guessing, I'm no InnoDB guru).

The only thing I wonder is why InnoDB would not use this for logging. I would expect the most benefit here. IMHO, every commit must be written to disk. So O_DIRECT should be good.

I would like to hear of your experiences if you find time to try this out.

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Re: MySQL + NAS(NFS) - Possible solution?
September 26, 2005 05:09AM


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