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From "Haohui Mai (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-6293) Issues with OIV processing PB-based fsimages
Date Sat, 10 May 2014 22:08:40 GMT

    [ https://issues.apache.org/jira/browse/HDFS-6293?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13992501#comment-13992501

Haohui Mai commented on HDFS-6293:

bq. In the results above, the amount of memory on the machine is far larger than the image
so everything happens in memory and seeks are free.

Reads on fsimage are mostly sequential, so it really doesn't matter whether the whole fsimage
can fit into the memory or not.

bq. Can you run an experiment with a large fsimage (25G or so) with a representative fs hierarchy
(not totally flat) and then generate DB and convert to LSR on a smaller machine (16G or so)?

The fsimage that I've experimented with originates from a production cluster. It was in the
old format which requires a big machine to do convert it to a PB-based fsimage. I have to
strip it down to fit it into my machine. Please see HDFS-5698 on how the image is generated.
If you can send me your PB-based fsimage then I can experiment with it.

Since the image comes from a production cluster, the fs hierarchy is definitely not flat.
I generated the DB by in a Java VM with 22G heap.

> Issues with OIV processing PB-based fsimages
> --------------------------------------------
>                 Key: HDFS-6293
>                 URL: https://issues.apache.org/jira/browse/HDFS-6293
>             Project: Hadoop HDFS
>          Issue Type: Bug
>    Affects Versions: 2.4.0
>            Reporter: Kihwal Lee
>            Assignee: Haohui Mai
>            Priority: Blocker
>         Attachments: HDFS-6293.000.patch, HDFS-6293.001.patch, HDFS-6293.002-save-deprecated-fsimage.patch,
Heap Histogram.html
> There are issues with OIV when processing fsimages in protobuf. 
> Due to the internal layout changes introduced by the protobuf-based fsimage, OIV consumes
excessive amount of memory.  We have tested with a fsimage with about 140M files/directories.
The peak heap usage when processing this image in pre-protobuf (i.e. pre-2.4.0) format was
about 350MB.  After converting the image to the protobuf format on 2.4.0, OIV would OOM even
with 80GB of heap (max new size was 1GB).  It should be possible to process any image with
the default heap size of 1.5GB.
> Another issue is the complete change of format/content in OIV's XML output.  I also noticed
that the secret manager section has no tokens while there were unexpired tokens in the original
image (pre-2.4.0).  I did not check whether they were also missing in the new pb fsimage.

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