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From "Tsz Wo (Nicholas), SZE (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-8352) Rename '.snapshot' directory
Date Tue, 16 Apr 2013 18:41:17 GMT

    [ https://issues.apache.org/jira/browse/HBASE-8352?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13633162#comment-13633162

Tsz Wo (Nicholas), SZE commented on HBASE-8352:

> If 2.0.5-alpha is the underlying hdfs, I think accessing .snapshot dir would not be allowed.

I thought hdfs snapshots dirs are readable and browseable just like normal dirs. Only direct
write operations would be blocked. Is this incorrect?

Jonathan, you are right that snapshot dirs are readable and browseable.  Let me clarify this:

With snapshot feature, dirs can be set as _snapshottable_ and snapshots can only be taken
on snapshottable dirs.  Once a dir (say /foo) is snapshottable, ".snapshot" is used for accessing
snapshot and the usual API/CLI will work for it, e.g.
- show all snapshots of foo
fs -ls /foo/.snapshot   
- list the file in snapshot s0
fs -ls /foo/.snapshot/s0
- copy a file inside s0 to /tmp
fs -cp /foo/.snapshot/s0/bar.txt /tmp

For non-snapshottable dir (say /bar), /bar/.snapshot is an non-existing file.  That's why
Ted got file not found from CLI.
> Rename '.snapshot' directory
> ----------------------------
>                 Key: HBASE-8352
>                 URL: https://issues.apache.org/jira/browse/HBASE-8352
>             Project: HBase
>          Issue Type: Bug
>            Reporter: Ted Yu
>            Assignee: Ted Yu
>            Priority: Blocker
>             Fix For: 0.98.0, 0.94.7, 0.95.1
>         Attachments: 8352-0.94-v1.txt, 8352-0.94-v2.txt, 8352-trunk.txt, 8352-trunk-v2.txt
> Testing HBase Snapshot on top of Hadoop's Snapshot branch (http://svn.apache.org/viewvc/hadoop/common/branches/HDFS-2802/),
we found that both features used '.snapshot' directory to store metadata.
> HDFS (built from HDFS-2802 branch) doesn't allow paths with .snapshot as a component
> From discussion on dev@hbase.apache.org, (see http://search-hadoop.com/m/kY6C3cXMs51),
consensus was to rename '.snapshot' directory in HBase so that both features can co-exist

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