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From Suresh Thalamati <tsur...@Source-Zone.org>
Subject Re: alligned Vs Non Alligned log writes ..
Date Mon, 13 Dec 2004 19:39:57 GMT
Mike Matrigali wrote:

>If java ever provides a way to directly queue I/O straight from
>our buffer to disk with no intermediate data copy then it may
>be important to use a page based log scheme.  For now it looks
>like the stream interfaces being used and the JVM's optimization
>of those interfaces are working ok.  A nice property of the current
>log which we don't take advantage of is that since it is a stream,
>we could dynamically change the size of the block of data we
>write, increasing it as log activity increases.  This sort of
>happens with group commit where we will write less than a block
>if a commit happens - but we never consider growing the buffers
>bigger than the boot time size.
>From the number it does  looks like performance is better is only in
some cases(64k) . Considering the
overhead involved in making writes aligned ,  like performing extra
writes to handle unfilled page
cases in short transactions.  By implementing alligned log writes , 
logn transaction perfomance
might improve but short transasction peformance is likely to degrade..

I agree  that it  may not be good idea to modify the logging system to
perform  alligned writes at least for now.


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