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 > >> >> >>> >> > > >> >> >>> >> > >> >> >>> > > >> >> >> > >> >> > > >> >> > > >> > > >> > > >> > > >
