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From Enis Söztutar <enis....@gmail.com>
Subject Re: collision in the naming of '.snapshot' directory between hdfs snapshot and hbase snapshot
Date Wed, 17 Apr 2013 17:59:06 GMT
Harsh, the discussion above includes the reasoning behind forcing the
change in hbase rather than hdfs. Although HBase has shipped with this,
HDFS's snapshots are user visible, meaning that you can do:

hadoop fs -ls /user/foo/.snapshot/

Plus, it is a convention for file systems (netapp, etc) to expose snapshots
this way, having a name ".snapshot". HBase's snapshot directories are not
user visible, and not widely used yet.

Enis


On Wed, Apr 17, 2013 at 9:14 AM, Andrew Purtell <apurtell@apache.org> wrote:

> Thanks for the consideration but we've just committed a change to address
> this as HBASE-8352
>
>
> On Wednesday, April 17, 2013, Harsh J wrote:
>
> > Pardon my late inquisition here but since HBase already shipped out
> > with a name .snapshots/, why do we force them to change it, and not
> > rename HDFS' snapshots to use .hdfs-snapshots, given that HDFS
> > Snapshots has not been released for any users yet. The way I see it,
> > that'd be much more easier to do than making a workaround for a done
> > deal on HBase, which already has its snapshot's users.
> >
> > @Tsz-Wo - If the snapshots in HDFS aren't a 'generic' feature
> > applicable to other FileSystem interface implementations as well, then
> > .hdfs-snapshots should be fine for it - no?
> >
> > On Wed, Apr 17, 2013 at 2:32 AM, Ted Yu <yuzhihong@gmail.com> wrote:
> > > Hi,
> > > Please take a look at patch v5 attached to HBASE-8352.
> > >
> > > It would be nice to resolve this blocker today so that 0.94.7 RC can be
> > cut.
> > >
> > > Thanks
> > >
> > > On Tue, Apr 16, 2013 at 10:12 AM, lars hofhansl <larsh@apache.org>
> > wrote:
> > >
> > >> Please see my last comment on the jira. We can make this work without
> > >> breaking users who are using HDFS snapshots.
> > >>
> > >>   ------------------------------
> > >>  *From:* Ted Yu <yuzhihong@gmail.com>
> > >> *To:* dev@hbase.apache.org
> > >> *Cc:* hdfs-dev@hadoop.apache.org; lars hofhansl <larsh@apache.org>
> > >> *Sent:* Tuesday, April 16, 2013 10:00 AM
> > >> *Subject:* Re: collision in the naming of '.snapshot' directory
> between
> > >> hdfs snapshot and hbase snapshot
> > >>
> > >> Let's get proper release notes for HBASE-8352 .
> > >>
> > >> Either Lars or I can send out notification to user mailing list so
> that
> > >> there is enough preparation for this change.
> > >>
> > >> Cheers
> > >>
> > >> On Tue, Apr 16, 2013 at 8:46 AM, Jonathan Hsieh <jon@cloudera.com>
> > wrote:
> > >>
> > >> I was away from keyboard when I asserted that hdfs snapshot was a
> hadoop
> > >> 2.1 or 3.0 feature.  Apparently it is targeted as a hadoop 2.0.5
> > feature.
> > >>  (I'm a little surprised -- expected this to be a hadoop2 compat
> > breaking
> > >> feature) -- so I agree that this is a bit more urgent.
> > >>
> > >> Anyway, I agree that the fs .snapshot naming convention is long
> standing
> > >> and should win.
> > >>
> > >> My concern is with breaking compatibility in 0.94 again -- if we don't
> > go
> > >> down the conf variable route,  I consider having docs to properly
> > document
> > >> how to do the upgrade and caveats of doing the upgrade in the
> > docs/release
> > >> notes blocker to hbase 0.94.7.  (specifically mentioning from 0.94.6
> to
> > >> 0.94.7, and to possibly to 0.95).
> > >>
> > >> Jon.
> > >>
> > >> On Mon, Apr 15, 2013 at 9:00 PM, Ted Yu <yuzhihong@gmail.com> wrote:
> > >>
> > >> > bq. Alternatively, we can detect the underlying Hadoop version, and
> > use
> > >> > either .snapshot or .hbase_snapshot in 0.94 depending on h1 &
h2.
> > >> >
> > >> > I think this would introduce more confusion, especially for
> > operations.
> > >> >
> > >> > Cheers
> > >> >
> > >> > On Mon, Apr 15, 2013 at 8:52 PM, Enis Söztutar <enis.soz@gmail.com>
> > >> wrote:
> > >> >
> > >> > > Because HDFS exposes the snapshots so that the normal file system
> > >> > > operations are mapped inside snapshot dirs, I think HDFS reserving
> > the
> > >> > > .snapshot name makes sense. OTOH, nothing is specific about the
> dir
> > >> name
> > >> > > that is chosen by HBase.
> > >> > >
> > >> > > I would prefer to change the dir name in 0.94 as well, since
0.94
> is
> > >> also
> > >> > > being run on top of hadoop 2. Alternatively, we can detect the
> > >> underlying
> > >> > > Hadoop version, and use either .snapshot or .hbase_snapshot in
> 0.94
> > >> > > depending on h1 & h2.
> > >> > >
> > >> > > Enis
> > >> > >
> > >> > >
> > >> > > On Mon, Apr 15, 2013 at 8:31 PM, Ted Yu <yuzhihong@gmail.com>
> > wrote:
> > >> > >
> > >> > > > bq. let's make the hbase snapshot for a conf variable.
> > >> > > >
> > >> > > > Once we decide on the new name of snapshot directory, we
should
> > still
> > >> > use
> > >> > > > hardcoded value. This aligns with current code base:
> > >> > > > See this snippet from HConstants:
> > >--
> > Harsh J
> >
>
>
> --
> Best regards,
>
>    - Andy
>
> Problems worthy of attack prove their worth by hitting back. - Piet Hein
> (via Tom White)
>

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