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https://issues.apache.org/jira/browse/HBASE-7660?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13562169#comment-13562169
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Jonathan Hsieh edited comment on HBASE-7660 at 1/25/13 12:08 AM:
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When HDFS upgrades incompatibly (hadoop1 -> hadoop2), it happens in is in
"upgrade mode" and "finalize" command that I assume forces everything to the
newer format. Once finalized, you can't go back but you should be safe to go
forward. Before finalized, I believe it continues to only write in the older
format. This feels like #3 (except front loaded instead of lazy before the
next upgrade).
We've actually run into some HFile format problems between 0.92 and 0.94
recently -- [~eclark]'s HBASE-7647, and I believe he's found another.
was (Author: jmhsieh):
When HDFS upgrades incompatibly (hadoop1 -> hadoop2), it happens in is in
"upgrade mode" and "finalize" command that I assume forces everything to the
newer format. Once finalized, you can't go back but you should be safe to go
forward. Before finalized, I believe it continues to only write in the new
format. This feels like #3 (except front loaded instead of lazy before the
next upgrade).
We've actually run into some HFile format problems between 0.92 and 0.94
recently -- [~eclark]'s HBASE-7647, and I believe he's found another.
> Remove HFileV1 code
> -------------------
>
> Key: HBASE-7660
> URL: https://issues.apache.org/jira/browse/HBASE-7660
> Project: HBase
> Issue Type: Improvement
> Components: hbck, HFile, migration
> Reporter: Matt Corgan
> Fix For: 0.96.0
>
>
> HFileV1 should be removed from the regionserver because it is somewhat of a
> drag on development for working on the lower level read paths. It's an
> impediment to cleaning up the Store code.
> V1 HFiles ceased to be written in 0.92, but the V1 reader was left in place
> so users could upgrade from 0.90 to 0.92. Once all HFiles are compacted in
> 0.92, then the V1 code is no longer needed. We then decided to leave the V1
> code in place in 0.94 so users could upgrade directly from 0.90 to 0.94. The
> code is still there in trunk but should probably be shown the door. I see a
> few options:
> 1) just delete the code and tell people to make sure they compact everything
> using 0.92 or 0.94
> 2) create a standalone script that people can run on their 0.92 or 0.94
> cluster that iterates the filesystem and prints out any v1 files with a
> message that the user should run a major compaction
> 3) add functionality to 0.96.0 (first release, maybe in hbck) that
> proactively kills v1 files, so that we can be sure there are none when
> upgrading from 0.96 to 0.98
> 4) punt to 0.98 and probably do one of the above options in a year
> I would vote for #1 or #2 which will allow us to have a v1-free 0.96.0.
> HFileV1 has already survived 2 major release upgrades which i think many
> would agree is more than enough for a pre-1.0, free product. If we can
> remove it in 0.96.0 it will be out of the way to introduce some nice
> performance improvements in subsequent 0.96.x releases.
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