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From:Jonas Oreland Date:April 6 2011 7:41am
Subject:Re: what is ndbinfo.diskpagebuffer.block_instance?
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On 04/06/11 09:36, Hendrik Woltersdorf wrote:
> 
> Hi,
> 
> I query ndbinfo.diskpagebuffer for hitratio as shown in
>
> http://dev.mysql.com/doc/mysql-cluster-excerpt/5.1/en/mysql-cluster-ndbinfo-diskpagebuffer.html
> 
> In different clusters I get a different number of rows per node-id
> depending on the number of "block_instance"s per node-id.
> 
> This column (block_instance) is not really documented for table
> diskpagebuffer. What does it mean here and is this information of any value
> for me?
> 
> regards
> 
> Hendrik Woltersdorf
> XCOM AG
> Email: Hendrik.Woltersdorf@stripped

In the multi-threaded data-node,
there are multiple instance of the disk-page-buffer-cache.

the "block_instance" show from which instance the numbers reported are.

> is this information of any value for me

i'd say no...

however, the suggested select to get hit-ratio, on link you provided
should be changed, to perform a group by node_id

e.g

SELECT node_id, 100 * SUM(page_requests_direct_return) / SUM(page_requests_direct_return +
page_requests_wait_io) AS hit_ratio
FROM ndbinfo.diskpagebuffer
GROUP BY node_id

/Jonas

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Thread
what is ndbinfo.diskpagebuffer.block_instance?Hendrik Woltersdorf6 Apr
  • Re: what is ndbinfo.diskpagebuffer.block_instance?Jonas Oreland6 Apr
    • Re: Re: what is ndbinfo.diskpagebuffer.block_instance?Hendrik Woltersdorf6 Apr
      • Re: what is ndbinfo.diskpagebuffer.block_instance?Jonas Oreland6 Apr