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https://issues.apache.org/jira/browse/HBASE-7987?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13593679#comment-13593679
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Ted Yu commented on HBASE-7987:
-------------------------------
bq. We can, but the idea behind the manifest is reducing the NN operation...
I think one manifest file per region is intuitive for both online and offline
snapshots. For HRegion.addRegionToSnapshot(), there is less coordination needed
in FlushSnapshotSubprocedure
bq. and if you add more manifest you end up in the same situation as before.
There is still considerable savings in manifest per region proposal.
Jesse expressed same idea in the first paragraph below:
https://issues.apache.org/jira/browse/HBASE-7360?focusedCommentId=13593535&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-13593535
> Snapshot Manifest file instead of multiple empty files
> ------------------------------------------------------
>
> Key: HBASE-7987
> URL: https://issues.apache.org/jira/browse/HBASE-7987
> Project: HBase
> Issue Type: Improvement
> Components: snapshots
> Reporter: Matteo Bertozzi
>
> Currently taking a snapshot means creating one empty file for each file in
> the source table directory, plus copying the .regioninfo file for each
> region, the table descriptor file and a snapshotInfo file.
> during the restore or snapshot verification we traverse the filesystem
> (fs.listStatus()) to find the snapshot files, and we open the .regioninfo
> files to get the information.
> to avoid hammering the NameNode and having lots of empty files, we can use a
> manifest file that contains the list of files and information that we need.
> To keep the RS parallelism that we have, each RS can write its own manifest.
> {code}
> message SnapshotDescriptor {
> required string name;
> optional string table;
> optional int64 creationTime;
> optional Type type;
> optional int32 version;
> }
> message SnapshotRegionManifest {
> optional int32 version;
> required RegionInfo regionInfo;
> repeated FamilyFiles familyFiles;
> message StoreFile {
> required string name;
> optional Reference reference;
> }
> message FamilyFiles {
> required bytes familyName;
> repeated StoreFile storeFiles;
> }
> }
> {code}
> {code}
> /hbase/.snapshot/<snapshotName>
> /hbase/.snapshot/<snapshotName>/snapshotInfo
> /hbase/.snapshot/<snapshotName>/<tableName>
> /hbase/.snapshot/<snapshotName>/<tableName>/tableInfo
> /hbase/.snapshot/<snapshotName>/<tableName>/regionManifest(.n)
> {code}
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