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https://issues.apache.org/jira/browse/HBASE-8370?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13694296#comment-13694296
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Varun Sharma commented on HBASE-8370:
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So, it seems that we have per block type metrics from SchemaMetrics under the
region server and they are exposed as /jmx.
The question is, which metric should we report on the region server UI. Right
now all our clusters 99 % cache hit ratio which is false, since 20 % percent of
the time there is a DataBlock miss and we are hitting disk for 20 % of requests.
I have been misled by this number in the past, and I think there could be
others, who are being similarly misled. So, should we just report another more
representative metric on the region server console.
Varun
> Report data block cache hit rates apart from aggregate cache hit rates
> ----------------------------------------------------------------------
>
> Key: HBASE-8370
> URL: https://issues.apache.org/jira/browse/HBASE-8370
> Project: HBase
> Issue Type: Improvement
> Components: metrics
> Reporter: Varun Sharma
> Assignee: Varun Sharma
> Priority: Minor
>
> Attaching from mail to [email protected]
> I am wondering whether the HBase cachingHitRatio metrics that the region
> server UI shows, can get me a break down by data blocks. I always see this
> number to be very high and that could be exagerated by the fact that each
> lookup hits the index blocks and bloom filter blocks in the block cache
> before retrieving the data block. This could be artificially bloating up the
> cache hit ratio.
> Assuming the above is correct, do we already have a cache hit ratio for data
> blocks alone which is more obscure ? If not, my sense is that it would be
> pretty valuable to add one.
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