Data balancing on hdfs is different to region balancing across your nodes. Maybe there is a bug in our balancer if there are only two nodes involved?
If there is nothing to balance, because its' already balanced, it'll output this: 2011-03-09 00:40:35,537 INFO org.apache.hadoop.hbase.master.LoadBalancer: Skipping load balancing. servers=5 regions=1007 average=201.4 mostloaded=202 leastloaded=202 ....else you will see: 2011-03-09 00:45:35,538 INFO org.apache.hadoop.hbase.master.LoadBalancer: Calculated a load balance in 1ms. Moving 1 regions off of 1 overloaded servers onto 0 less loaded servers 2011-03-09 00:45:35,538 INFO org.apache.hadoop.hbase.master.HMaster: balance hri=usertable,user362822713,1299624789204.1720a98e1a0709e9a401a8eb9d8436bc., src=sv4borg230,61020,1299616745209, dest=sv4borg234,61020,1299616745224 2011-03-09 00:45:35,538 DEBUG org.apache.hadoop.hbase.master.AssignmentManager: Starting unassignment of region usertable,user362822713,1299624789204.1720a98e1a0709e9a401a8eb9d8436bc. (offlining) ... or there will be a message that it is skipping balancing because there are regions in movement already. Do you see none of the above? In the shell you can run the balancer explicitly. hbase> balance Watch the master logs while this is happening. What does it say? St.Ack On Mon, Mar 14, 2011 at 6:27 PM, Weiwei Xiong <xion...@gmail.com> wrote: > On Mon, Mar 14, 2011 at 4:09 PM, Bill Graham <billgra...@gmail.com> wrote: > >> I hope I'm not hijacking the thread but I'm seeing what I think is a >> similar issue. About a week ago I loaded a bunch of data into a newly >> created table. It took about an hour and resulted in 12 regions being >> created on a single node. (Afterwards I remembered a conversation with >> JD where he described this behavior and how you could pre-create at >> least N regions where N is your number of nodes to get better >> distribution off the bat). >> >> Some following questions. Do we have to pre-create N regions on different > nodes to get better distribution? I ask this because I also noticed that > HBase prefer to always store new key-values on one node. Now I know > that we can do major compactions to rebalance the data. But it would be > better if the data could be stored on less-loaded nodes at time it is > inserted. > This makes I/O more balanced I guess. > > > >> Anyway, it's been about a week and all regions for the table are still >> on 1 node. I see messages like this in the logs every 5 minutes: >> >> 2011-03-14 15:59:03,148 INFO >> org.apache.hadoop.hbase.master.LoadBalancer: Skipping load balancing. >> servers=4 regions=62 average=15.5 mostloaded=16 leastloaded=16 >> >> It seems the total regions are evenly balanced, but individual tables >> are not. Where should I look to troubleshoot why this table's regions >> (as well as others) aren't evenly distributed? I'd guess that I can >> major compact all tables to fix it, but I'd like to figure out why it >> hasn't happened automatically. >> >> HBase 0.90.0 >> CDH3b2 >> >> thanks, >> Bill >> >> On Mon, Mar 14, 2011 at 3:31 PM, Weiwei Xiong <xion...@gmail.com> wrote: >> > I see. Thanks Ryan. >> > >> > -- Weiwei >> > >> > On Mon, Mar 14, 2011 at 3:28 PM, Ryan Rawson <ryano...@gmail.com> wrote: >> > >> >> by default runs 1x/day. you can do it manually in the hbase shell by >> >> typing: >> >> >> >> hbase(main):001:0> major_compact "table_name" >> >> >> >> -ryan >> >> >> >> >> >> On Mon, Mar 14, 2011 at 3:25 PM, Weiwei Xiong <xion...@gmail.com> >> wrote: >> >> > Thanks for your info Ryan. >> >> > Does HBase do major compaction regularly or do I need to manually do >> >> this? >> >> > If it's automatic, how frequently is it performed? >> >> > I am running 1 replication. >> >> > Thanks, >> >> > -- Weiwei >> >> > >> >> > On Mon, Mar 14, 2011 at 3:18 PM, Ryan Rawson <ryano...@gmail.com> >> wrote: >> >> >> >> >> >> HDFS does the data rebalancing, over time as major compactions and >> new >> >> >> data comes in, files are written first to the local node then to >> >> >> remote nodes. >> >> >> >> >> >> Whats the replication factor you are running? HDFS on 2 nodes is >> >> >> tricky, since you can either choose r=1 (no data protection) or r=2 >> >> >> (all writes go to both nodes). >> >> >> >> >> >> The sweet spot is above 6 nodes alas. >> >> >> >> >> >> -ryan >> >> >> >> >> >> On Mon, Mar 14, 2011 at 3:12 PM, Weiwei Xiong <xion...@gmail.com> >> >> wrote: >> >> >> > Sorry I forgot to mention. I am using HBase 0.90.1 over HDFS >> >> 0.20.append >> >> >> > Thanks, >> >> >> > -- Weiwei >> >> >> > >> >> >> > On Mon, Mar 14, 2011 at 3:10 PM, Weiwei Xiong <xion...@gmail.com> >> >> wrote: >> >> >> >> >> >> >> >> Thanks very much for your replies. >> >> >> >> Something was unclear in my previous emails. I had one node >> started >> >> >> >> first >> >> >> >> and another was added in later. And there're already some regions >> >> >> >> created in >> >> >> >> the first started node. Then I started to import more data into >> the >> >> >> >> same >> >> >> >> table and found that it's always the first node that keeps serving >> >> the >> >> >> >> data >> >> >> >> writes. >> >> >> >> Actually I was expecting that the region data would be re-balanced >> to >> >> >> >> another data node. And I did see in the master log that HBase >> master >> >> is >> >> >> >> trying to unassigning some regions from the overloaded node and >> >> >> >> re-assign >> >> >> >> them to the less-loaded node. But the real data was never >> migrated. >> >> >> >> I think I observed the region index and cache rebalancing from the >> >> >> >> master >> >> >> >> log (correct me if I were wrong). Does anyone know how frequently >> >> this >> >> >> >> happens? >> >> >> >> Another question is, does HBase support data and I/O rebalancing? >> Or >> >> I >> >> >> >> should rely on HDFS to do data rebalancing? I guess HBase should >> also >> >> >> >> support data rebalancing otherwise every time I restart HBase the >> >> >> >> regions >> >> >> >> will have to be rebalanced again. Will someone tell me how to >> >> configure >> >> >> >> or >> >> >> >> program HBase to do data rebalancing? >> >> >> >> Thanks, >> >> >> >> -- Weiwei >> >> >> >> On Mon, Mar 14, 2011 at 2:43 PM, Ryan Rawson <ryano...@gmail.com> >> >> >> >> wrote: >> >> >> >>> >> >> >> >>> What version of HBase are you testing? >> >> >> >>> >> >> >> >>> Is it literally 0 vs N assignments? >> >> >> >>> >> >> >> >>> On Mon, Mar 14, 2011 at 1:18 PM, Weiwei Xiong <xion...@gmail.com >> > >> >> >> >>> wrote: >> >> >> >>> > Thanks! >> >> >> >>> > >> >> >> >>> > I checked the master log and found some info like this: >> >> >> >>> > " timestamp ***, INFO org.apache.hadoop.hbase.master.HMaster: >> >> >> >>> > balance >> >> >> >>> > hri=***, src=***, dst=*** " >> >> >> >>> > >> >> >> >>> > So I assume the balancer is running. There's no failing info >> >> there, >> >> >> >>> > but >> >> >> >>> > I >> >> >> >>> > didn't see the regions were actually balanced as the log >> states. >> >> >> >>> > >> >> >> >>> > Is it possible that I have been keeping dumping data into the >> >> table >> >> >> >>> > thus the >> >> >> >>> > balancing won't work? >> >> >> >>> > >> >> >> >>> > Thanks, >> >> >> >>> > -- Weiwei >> >> >> >>> > >> >> >> >>> > On Mon, Mar 14, 2011 at 12:15 PM, Stack <st...@duboce.net> >> wrote: >> >> >> >>> > >> >> >> >>> >> Check the master log. See if the load balancer is running or >> >> not. >> >> >> >>> >> It >> >> >> >>> >> usually runs every 5 minutes by default. It may not run if >> >> regions >> >> >> >>> >> are transitioning. It'll log regardless. >> >> >> >>> >> >> >> >> >>> >> St.Ack >> >> >> >>> >> >> >> >> >>> >> On Mon, Mar 14, 2011 at 10:50 AM, Weiwei Xiong < >> >> xion...@gmail.com> >> >> >> >>> >> wrote: >> >> >> >>> >> > Hi, >> >> >> >>> >> > >> >> >> >>> >> > I recently set up a 2-node Hadoop and HBase cluster and am >> >> trying >> >> >> >>> >> > to >> >> >> >>> >> > load >> >> >> >>> >> > data into my HBase table using HBase client. >> >> >> >>> >> > >> >> >> >>> >> > The issue bothers me is that the data are always written >> into >> >> one >> >> >> >>> >> > node of >> >> >> >>> >> > the cluster, i.e., all the regions of the hbase table are on >> >> one >> >> >> >>> >> > node. >> >> >> >>> >> > >> >> >> >>> >> > Is there any configuration I need to change for make the >> load >> >> >> >>> >> > balanced? >> >> >> >>> >> > >> >> >> >>> >> > Thanks, >> >> >> >>> >> > -- w >> >> >> >>> >> > >> >> >> >>> >> >> >> >> >>> > >> >> >> >> >> >> >> > >> >> >> > >> >> > >> >> > >> >> >> > >> >
