Thanks for the info. I will do the "group by".

regards

Hendrik Woltersdorf
XCOM AG
Email: Hendrik.Woltersdorf@xcom.de




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Vorsitzender des Aufsichtsrates: Stefan H. TarachInactive hide details for Jonas Oreland ---06.04.2011 09:44:50---On 04/06/11 09:36, Hendrik Woltersdorf wrote:Jonas Oreland ---06.04.2011 09:44:50---On 04/06/11 09:36, Hendrik Woltersdorf wrote:

          Jonas Oreland <jonas.oreland@oracle.com>

          06.04.2011 09:41

An

Hendrik Woltersdorf <hendrik.woltersdorf@xcom.de>

Kopie

Cluster <cluster@lists.mysql.com>

Thema

Re: what is ndbinfo.diskpagebuffer.block_instance?

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@xcom.de

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