Apache
/
hbase
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

HBASE-8596 [docs] Add docs about RegionServer "draining" mode 

git-svn-id: https://svn.apache.org/repos/asf/hbase/trunk@1485442 13f79535-47bb-0310-9956-ffa450edef68
This commit is contained in:
Jonathan Hsieh 2013-05-22 21:39:46 +00:00
parent e2f57c7696
commit f30ee5fac6
1 changed files with 31 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

32
src/main/docbkx/ops_mgt.xml
View File

@ -419,13 +419,37 @@ false
</para>
</note>
</para>
<section xml:id="draining.servers">
<title>Decommissioning several Regions Servers concurrently</title>
<para>If you have a large cluster, you may want to
decomission more than one machines at a time by gracefully
stopping mutiple RegionServers concurrently.
</para>
<para>To gracefully drain multiple regionservers at the
same time, RegionServers can be put into a "draining"
state. This is done by marking a RegionServer as a
draining node by creating an entry in ZooKeeper under the
hbase_root/draining znode. This znode has format
"name,port,startcode" just like the regionserver entries
under hbase_root/rs znode.
</para>
<para>Without this, when decommissioning mulitple nodes
may be non-optimal because regions that are being drained
from one region server may be moved to other regions that
are also draining. Marking RegionServers to be in the
draining state prevents this from happening. <note>See
this <link xlink:href="http://inchoate-clatter.blogspot.com/2012/03/hbase-ops-automation.html">blog
post</link> for more details. </note>
</para>
</section>
<section xml:id="bad.disk">
<title>Bad or Failing Disk</title>
<para>It is good having <xref linkend="dfs.datanode.failed.volumes.tolerated" /> set if you have a decent number of disks
per machine for the case where a disk plain dies. But usually disks do the "John Wayne" -- i.e. take a while
to go down spewing errors in <filename>dmesg</filename> -- or for some reason, run much slower than their
companions. In this case you want to decommission the disk. You have two options. You can
<xlink href="http://wiki.apache.org/hadoop/FAQ#I_want_to_make_a_large_cluster_smaller_by_taking_out_a_bunch_of_nodes_simultaneously._How_can_this_be_done.3F">decommission the datanode</xlink>
<link xlink:href="http://wiki.apache.org/hadoop/FAQ#I_want_to_make_a_large_cluster_smaller_by_taking_out_a_bunch_of_nodes_simultaneously._How_can_this_be_done.3F">decommission the datanode</link>
or, less disruptive in that only the bad disks data will be rereplicated, can stop the datanode,
unmount the bad volume (You can't umount a volume while the datanode is using it), and then restart the
datanode (presuming you have set dfs.datanode.failed.volumes.tolerated > 0). The regionserver will
@ -489,6 +513,12 @@ false
</listitem>
</orderedlist>
</para>
<para>It is important to drain HBase regions slowly when
restarting regionservers. Otherwise, multiple regions go
offline simultaneously as they are re-assigned to other
nodes. Depending on your usage patterns, this might not be
desirable.
</para>
</section>
<section xml:id="adding.new.node">
<title>Adding a New Node</title>