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https://issues.apache.org/jira/browse/HDFS-2802?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13489564#comment-13489564
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Aaron T. Myers commented on HDFS-2802:
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[~sanjay.radia]
bq. wrt to your alternate proposal, folks can get confused about which of the
two series of documents matched the patches in the Jira. Can you please rename
yours as snapshot-alternate-design-proposal.{tex,pdf} and also reflect that in
the title inside the document.
Sure, I'll name the files differently from now on, though my hope is to get us
collaborating on a single design document, hence why I uploaded the .tex file
as well. As Konst points out, the two design proposals are currently very close
to each other.
[~shv]
bq. Not sure how you will handle the snapshot deletion in the middle of the
range. Say you have snapshots 1 through 5, and then delete snapshot 3.
I agree that this should be discussed more in the document. The idea is that to
delete a snapshot from the perspective of the client, we'd only need to remove
the info about that snapshot from the given snapshottable directory. That could
be done in constant time, and clients would no longer be able to access that
snapshot at that moment. Actual cleanup of files/directories which are no
longer referenced by any snapshot could then be done synchronously or
asynchronously at the NameNode.
bq. The idea of monotonously increasing snapshot ids seems to be the only major
diversion of your design from Suresh & Co. No doubt it should be discussed in
details, but does that justify/qualify-for submitting an alternative design.
I agree that the latest posted design doc is very close to the ones posted by
Suresh and Nicholas, but that was exactly the point - I was proposing a merged
design that incorporated parts of both. I would've just posted an updated doc
which modifies the previously posted proposal, as we often do with .patch files
containing code, but that's difficult to do when only the .pdf is uploaded,
hence why I posted an entirely different document.
bq. You don't want to start Apache Hadoop design-document-wars here, do you?
Certainly not. I'm trying to collaborate on the design. The latest one I posted
is an attempt at that.
> Support for RW/RO snapshots in HDFS
> -----------------------------------
>
> Key: HDFS-2802
> URL: https://issues.apache.org/jira/browse/HDFS-2802
> Project: Hadoop HDFS
> Issue Type: New Feature
> Components: data-node, name-node
> Reporter: Hari Mankude
> Assignee: Hari Mankude
> Attachments: HDFS-2802.20121101.patch,
> HDFS-2802-meeting-minutes-121101.txt, HDFSSnapshotsDesign.pdf, snap.patch,
> snapshot-design.pdf, snapshot-design.tex, snapshot-one-pager.pdf,
> Snapshots20121018.pdf, Snapshots20121030.pdf
>
>
> Snapshots are point in time images of parts of the filesystem or the entire
> filesystem. Snapshots can be a read-only or a read-write point in time copy
> of the filesystem. There are several use cases for snapshots in HDFS. I will
> post a detailed write-up soon with with more information.
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