[jira] [Commented] (HBASE-15248) BLOCKSIZE 4k should result in 4096 bytes on disk; i.e. fit inside a BucketCache 'block' of 4k

["Anoop Sam John (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HBASE-15248?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15753974#comment-15753974 ] 

Anoop Sam John commented on HBASE-15248:
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BC is having diff sized buckets and slots in it.  This sizes as per the possible HFile block sizes.  By def we consider 4K, 8K...  512K..  But we give an additional +1KB size for each of the bucket size and so to a slot..  So a 4K is actually becoming 5K.  And ya extra bytes are taken off by this cur header and next block header.
So right now u have removed the eager fetch of next block header right? [~saint.ack@gmail.com]..
Still the cur block, header we will need?
Am trying to solve issues under the parent so that I can make HBASE-17204 to happen.

> BLOCKSIZE 4k should result in 4096 bytes on disk; i.e. fit inside a BucketCache 'block' of 4k
> ---------------------------------------------------------------------------------------------
>
>                 Key: HBASE-15248
>                 URL: https://issues.apache.org/jira/browse/HBASE-15248
>             Project: HBase
>          Issue Type: Sub-task
>          Components: BucketCache
>            Reporter: stack
>
> Chatting w/ a gentleman named Daniel Pol who is messing w/ bucketcache, he wants blocks to be the size specified in the configuration and no bigger. His hardware set ups fetches pages of 4k and so a block that has 4k of payload but has then a header and the header of the next block (which helps figure whats next when scanning) ends up being 4203 bytes or something, and this then then translates into two seeks per block fetch.
> This issue is about what it would take to stay inside our configured size boundary writing out blocks.
> If not possible, give back better signal on what to do so you could fit inside a particular constraint.



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