[jira] [Commented] (HBASE-8369) MapReduce over snapshot files

["Enis Soztutar (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HBASE-8369?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13805748#comment-13805748 ] 

Enis Soztutar commented on HBASE-8369:
--------------------------------------

Uploaded the slides about this issue here: http://www.slideshare.net/enissoz/mapreduce-over-snapshots. It also contains some numbers for performaance comparison. 
Here are the raw numbers (in MB/s)

||Data size||	6.6 G||	13.2G||	19.8 G||	26.4 G||
|StoreFileCount per region|	3|	6|	9|	12|
|Scan	|8.2	|7.6	|11.2	|7.2|
|SnapshotScan	|60.8	|59.5	|55.3	|46.7|
|ScanMR	|75.9	|80.4	|82.3	|140.7|
|SnapshotScanMR	|198.6	|275.6	|311.6	|329.4|

Main takeaway, seems to be the single scanner speeds improve 5-6x, from 11MB/s to 55MB/s. That is also half of raw disk speed (for a single disk). Do not read much into MR test speed improvements when store file increases. That is due to job launch costs taking relatively smaller percentage when data sizes increase. 

> MapReduce over snapshot files
> -----------------------------
>
>                 Key: HBASE-8369
>                 URL: https://issues.apache.org/jira/browse/HBASE-8369
>             Project: HBase
>          Issue Type: New Feature
>          Components: mapreduce, snapshots
>            Reporter: Enis Soztutar
>            Assignee: Enis Soztutar
>             Fix For: 0.98.0
>
>         Attachments: HBASE-8369-0.94.patch, HBASE-8369-0.94_v2.patch, HBASE-8369-0.94_v3.patch, HBASE-8369-0.94_v4.patch, HBASE-8369-0.94_v5.patch, HBASE-8369-trunk_v1.patch, HBASE-8369-trunk_v2.patch, HBASE-8369-trunk_v3.patch, hbase-8369_v0.patch
>
>
> The idea is to add an InputFormat, which can run the mapreduce job over snapshot files directly bypassing hbase server layer. The IF is similar in usage to TableInputFormat, taking a Scan object from the user, but instead of running from an online table, it runs from a table snapshot. We do one split per region in the snapshot, and open an HRegion inside the RecordReader. A RegionScanner is used internally for doing the scan without any HRegionServer bits. 
> Users have been asking and searching for ways to run MR jobs by reading directly from hfiles, so this allows new use cases if reading from stale data is ok:
>  - Take snapshots periodically, and run MR jobs only on snapshots.
>  - Export snapshots to remote hdfs cluster, run the MR jobs at that cluster without HBase cluster.
>  - (Future use case) Combine snapshot data with online hbase data: Scan from yesterday's snapshot, but read today's data from online hbase cluster. 



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