On that new of a kernel you'll also need to increase your epoll limit. Some tips about that here:
http://www.cloudera.com/blog/2009/03/configuration-parameters-what-can-you-just-ignore/ Thanks -Todd On Wed, Nov 17, 2010 at 9:10 AM, Lars George <lars.geo...@gmail.com> wrote: > Are you running on EC2? Couldn't you simply up the heap size for the > java processes? > > I do not think there is a hard and fast rule to how many xcievers you > need, trial and error is common. Or ifmyou have enough heap simply set > it too high, like 4096 and that usually works fine. It all depends on > how many regions and column families you have on each server. > > Lars > > On Wed, Nov 17, 2010 at 5:31 PM, Lucas Nazário dos Santos > <nazario.lu...@gmail.com> wrote: > > I'm using Linux, the Amazon beta version that they recently released. I'm > > not very familiar with Linux, so I think the kernel version > > is 2.6.34.7-56.40.amzn1.x86_64. Hadoop version is 0.20.2 and HBase > version > > is 0.20.6. Hadoop and HBase have 2 GB each and they are not sawpping. > > > > Besides all other questions I posed, I have one more. How can I calculate > > the maximum number of xcievers? Is there a formula? > > > > Lucas > > > > > > > > On Wed, Nov 17, 2010 at 2:12 PM, Lars George <lars.geo...@gmail.com> > wrote: > > > >> Hi Lucas, > >> > >> What OS are you on? What kernel version? What is your Hadoop and HBase > >> version? How much heap do you assign to each Java process? > >> > >> Lars > >> > >> On Wed, Nov 17, 2010 at 3:05 PM, Lucas Nazário dos Santos > >> <nazario.lu...@gmail.com> wrote: > >> > Hi, > >> > > >> > This problem is widely know, but I'm not able to come up with a decent > >> > solution for it. > >> > > >> > I'm scanning 1.000.000+ rows from one table in order to index their > >> content. > >> > Each row has around 100 KB. The problem is that I keep getting the > >> > exception: > >> > > >> > Exception in thread > >> "org.apache.hadoop.dfs.datanode$dataxceiveser...@82d37" > >> > java.lang.OutOfMemoryError: unable to create new native thread > >> > > >> > This is a Hadoop exception and it causes the DataNote to go down, so I > >> > decreased the dfs.datanode.max.xcievers from 4048 to 512. Well, that > led > >> me > >> > to another problem: > >> > > >> > java.io.IOException: xceiverCount 513 exceeds the limit of concurrent > >> > xcievers 512 > >> > > >> > This time the DataNode doesn't die, nor HBase, but my scan, and the > whole > >> > indexing process, suffers a lot. > >> > > >> > After reading different posts about this issue, I have the impression > >> that > >> > HBase can't handle this limits transparently for the user. The scanner > is > >> a > >> > sequential process, so I thought it would free Hadoop resources > already > >> used > >> > in order to make room for new requests for data under HDFS. What I am > >> > missing? Should I slow down the scanning process? Should I scan > portions > >> of > >> > the table sequentially instead of doing a full scan in all 1.000.000+ > >> rows? > >> > Is there a timeout so unused Hadoop resources can be released? > >> > > >> > Thanks in advance, > >> > Lucas > >> > > >> > > > -- Todd Lipcon Software Engineer, Cloudera
