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https://issues.apache.org/jira/browse/HBASE-6055?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13292852#comment-13292852
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Jonathan Hsieh commented on HBASE-6055:
---------------------------------------
I still a bit confused -- still at the basic admin level. I think it would
help if we give the "restoring"/"export" parts some more attention and talk
about usage as opposed to mechanism first. I'm going to pose some use
case/examples/scenarios which hopefully will be easier to discuss.
Let's say I am an admin, and we are pre hdfs hardlinks.
I issue a "snapshot" command at the shell/master.
* HBase creates a new .snapshot subdir, and it contains references to HLogs and
HFiles. This is a "snapshot"
** This step is called: snapshotting, "taking a snapshot", and also
materializing right?
I currently have a snapshot. I want read-only access its contents to compare
with the current table.
* Does HBase know how to interpret the stuff in a .snapshot dir such that it
act like a read-only table?
* Do I, as an admin, need to execute some step to make it appear in HBase as a
read-only table? (if so what is this called?)
I currently have a snapshot. Oops! I accidentally truncated the table I had
snapshotted. I don't want the truncated version of the table anymore and I
want to replace the table with the snapshot so I have read write access.
* This is called "restoring" the snapshot right? (and I do this by issuing a
something like "restore" command at the shell?)
* Does HBase copy or move the data referred to in the snapshot?
I currently have a snapshot. I want the current version but I'd like to clone
of the snapshotted table that provides read/write access to the clone.
* Is/should this be supported?
* Is this called "restoring" or "exporting" the snapshot (to a new name)?
* For this to work I need to convert all references into actual copies of the
HFiles and HLogs right? Is this conversion called exporting? (FYI, this is
what I meant materializing to mean, but let's just stick to your definitions)
I currently have a snapshot. I want to send a copy of the snapshot to a remote
cluster so that it can provide read/write access to the data.
* Is/should this be supported?
* Do both HBase instances need to be up at the same time?
** This process would need to dereference the snapshot's references and copy
them. What is it called? exporting?
----
Source of confusion
bq. Export is taking a snapshot from the .snapshot/ directory and possibly
having a special snapshot distcp to somewhere. I would consider materialization
as taking the exported snapshot and then 'hooking it back up' to another
cluster (or the same) as a new table. You could throw materialization of the
exported snapshot, but they are in fact distinct.
I think the first "materialization" is supposed to be "restoration" yeah? I
don't quite get the last sentence.
> Snapshots in HBase 0.96
> -----------------------
>
> Key: HBASE-6055
> URL: https://issues.apache.org/jira/browse/HBASE-6055
> Project: HBase
> Issue Type: New Feature
> Components: client, master, regionserver, zookeeper
> Reporter: Jesse Yates
> Assignee: Jesse Yates
> Fix For: 0.96.0
>
> Attachments: Snapshots in HBase.docx
>
>
> Continuation of HBASE-50 for the current trunk. Since the implementation has
> drastically changed, opening as a new ticket.
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