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From "Colin Patrick McCabe (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-2802) Support for RW/RO snapshots in HDFS
Date Sat, 20 Oct 2012 21:32:15 GMT

    [ https://issues.apache.org/jira/browse/HDFS-2802?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13480836#comment-13480836
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Colin Patrick McCabe commented on HDFS-2802:
--------------------------------------------

Suresh said:

bq. How do [other filesystems] handle disk quota use when the original file is deleted and
only snapshots exists? That is the reason why counting the disk quota makes sense.

ZFS has "quotas" and "refquotas".  The former includes snapshot overhead; the latter does
not.  Based on some Googling, I think that on NetApp devices, quotas do not include snapshot
overhead.  (at least by default).  I think it makes sense to offer both kinds of quota, although
we don't have to implement them both right away, of course.
                
> 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: snap.patch, snapshot-one-pager.pdf, Snapshots20121018.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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