Major compaction does not do any "checking" for current file locations. Rather, major compactions take all files of a region and compact them into a single file per family. By rewriting the region to HDFS, all blocks will be written to the local node. That's how it gives locality.
By default, major compactions are run every 24 hours. JG > -----Original Message----- > From: Jamie Cockrill [mailto:[email protected]] > Sent: Thursday, July 08, 2010 3:24 PM > To: [email protected] > Subject: Re: HBase on same boxes as HDFS Data nodes > > Hi Venkatesh, > > I've had a read of the article that JD suggested and I think the > following is useful for your situation (it's the paragraph before the > last): > > "So this means for HBase that as the region server stays up for long > enough (which is the default) that after a major compaction on all > tables - which can be invoked manually or is triggered by a > configuration setting - it has the files local on the same host. The > data node that shares the same physical host has a copy of all data > the region server requires. If you are running a scan or get or any > other use-case you can be sure to get the best performance." > > If I understand this correctly, if you do a major compaction on the > table, it'll check that the data blocks and regions are co-located > properly and move any that are not. You can do a major compact in the > hbase shell manually with: > > major_compact '<your tablename here>' > > Without the angle brackets, but with the parentheses. I think it does > do major compacts on a periodic basis, but I couldn't say for sure. > > Thanks, > > Jamie > > PS, JD, thanks for the tip about locality. I'll get the hang of HBase > some point! > > On 8 July 2010 18:51, <[email protected]> wrote: > > > > Thankyou.. > > I've some more questions > > I'm spending quite a bit over last few weeks to develop one of our > applications using HBase/Hadoop > > & using 0.20.4 > > > > Hbase - Table X > > rows - 1- 100 -> Region A -> RegionServer A --> DataNode A > > .... > > rows 1500 - 1600 -> Region M -> RegionServer B -> DataNode B > > > > So based on what I have read so far..I'm thinking of Region Server A > & Data Node A pairs on the same host to > > make use of locality.. > > > > As per your answer ..If we restart the cluster, because of radom > assigment, locality is gone > > so..Region Server B -..> Region A ---> data blocks will be in Data > Node A > > ...if I understand correctly.. > > will the data move over time though...for example if i have lots of > access to data in DataNode A ? without the current work that is in > progress.. > > > > thanks again for your reply > > > > venkatesh > > > > > > > > > > > > > > > > > > -----Original Message----- > > From: Jean-Daniel Cryans <[email protected]> > > To: [email protected] > > Sent: Thu, Jul 8, 2010 1:35 pm > > Subject: Re: HBase on same boxes as HDFS Data nodes > > > > > > Former, " Now imagine you stop HBase after saving a lot of data and > > > > restarting it subsequently. The region servers are restarted and > > > > assign a seemingly random number of regions" > > > > > > > > It's not really because we enjoy it that way, but because the work > > > > required just isn't done. If this is of interest to you, Jonathan and > > > > Karthik at Facebook started rewriting our load balancer. See > > > > https://issues.apache.org/jira/browse/HBASE-2699 and > > > > https://issues.apache.org/jira/browse/HBASE-2480 > > > > > > > > J-D > > > > > > > > On Thu, Jul 8, 2010 at 10:30 AM, <[email protected]> wrote: > > > >> > > > >> Hi > > > >> Fairly new to hbase..& the list serve..Following up on this thread & > the > > > > article.. > > > >> Could some one elaborate why locality is lost upon restart? Is it > because > > > >> of random assignment by HMaster and/or HRegionServer is stateless or > other > > > > reasons? > > > >> > > > >> thanks > > > >> venkatesh > > > >> > > > >> > > > >> > > > >> > > > >> > > > >> > > > >> > > > >> > > > >> > > > >> > > > >> -----Original Message----- > > > >> From: Jean-Daniel Cryans <[email protected]> > > > >> To: [email protected] > > > >> Sent: Thu, Jul 8, 2010 1:11 pm > > > >> Subject: Re: HBase on same boxes as HDFS Data nodes > > > >> > > > >> > > > >> More info on this blog post: > > > >> > > > >> http://www.larsgeorge.com/2010/05/hbase-file-locality-in-hdfs.html > > > >> > > > >> > > > >> > > > >> J-D > > > >> > > > >> > > > >> > > > >> On Thu, Jul 8, 2010 at 10:11 AM, Jean-Daniel Cryans > <[email protected]> > > > > wrote: > > > >> > > > >>> This would be done at the expense of network IO, since you will > lose > > > >> > > > >>> locality for jobs that read/write to HBase. Also I guess the > datanodes > > > >> > > > >>> are also there, so HBase will lose locality with HDFS. > > > >> > > > >>> > > > >> > > > >>> J-D > > > >> > > > >>> > > > >> > > > >>> On Thu, Jul 8, 2010 at 10:07 AM, Jamie Cockrill > > > >> > > > >>> <[email protected]> wrote: > > > >> > > > >>>> Thanks all for your help with this, everything seems much more > stable > > > >> > > > >>>> for the meantime. I have a backlog loading job to run over a great > > > >> > > > >>>> deal of data, so I might separate out my region servers from my > task > > > >> > > > >>>> trackers for the meantime. > > > >> > > > >>>> > > > >> > > > >>>> Thanks again, > > > >> > > > >>>> > > > >> > > > >>>> Jamie > > > >> > > > >>>> > > > >> > > > >>>> > > > >> > > > >>>> > > > >> > > > >>>> On 8 July 2010 17:46, Jean-Daniel Cryans <[email protected]> > wrote: > > > >> > > > >>>>> OS cache is good, glad you figured out your memory problem. > > > >> > > > >>>>> > > > >> > > > >>>>> J-D > > > >> > > > >>>>> > > > >> > > > >>>>> On Thu, Jul 8, 2010 at 2:03 AM, Jamie Cockrill > <[email protected]> > > > >> > > > >> wrote: > > > >> > > > >>>>>> Morning all. Day 2 begins... > > > >> > > > >>>>>> > > > >> > > > >>>>>> I discussed this with someone else earlier and they pointed out > that > > > >> > > > >>>>>> we also have task trackers running on all of those nodes, which > will > > > >> > > > >>>>>> affect the amount of memory being used when jobs are being run. > Each > > > >> > > > >>>>>> tasktracker had a maximum of 8 maps and 8 reduces configured per > node, > > > >> > > > >>>>>> with a JVM Xmx of 512mb each. Clearly this implies a fully > utilised > > > >> > > > >>>>>> node will use 8*512mb + 8*512mb = 8GB of memory on tasks alone. > That's > > > >> > > > >>>>>> before the datanode does anything, or HBase for that matter. > > > >> > > > >>>>>> > > > >> > > > >>>>>> As such, I've dropped it to 4 maps, 4 reduces per node and > reduced the > > > >> > > > >>>>>> Xmx to 256mb, giving a potential maximum task overhead of 2GB > per > > > >> > > > >>>>>> node. Running 'vmstat 20' now, under load from mapreduce jobs, > > > >> > > > >>>>>> suggests that the actual free memory is about the same, but the > memory > > > >> > > > >>>>>> cache is much much bigger, which presumably is healthlier as, in > > > >> > > > >>>>>> theory, that ought to relinquish memory to processes that > request it. > > > >> > > > >>>>>> > > > >> > > > >>>>>> Lets see if that does the trick! > > > >> > > > >>>>>> > > > >> > > > >>>>>> ta > > > >> > > > >>>>>> > > > >> > > > >>>>>> Jamie > > > >> > > > >>>>>> > > > >> > > > >>>>>> > > > >> > > > >>>>>> On 7 July 2010 19:30, Jean-Daniel Cryans <[email protected]> > wrote: > > > >> > > > >>>>>>> YouAreDead means that the region server's session was expired, > GC > > > >> > > > >>>>>>> seems like your major problem. (file problems can happen after > a GC > > > >> > > > >>>>>>> sleep because they were moved around while the process was > sleeping, > > > >> > > > >>>>>>> you also get the same kind of messages with xcievers issue... > sorry > > > >> > > > >>>>>>> for the confusion) > > > >> > > > >>>>>>> > > > >> > > > >>>>>>> By over committing the memory I meant trying to fit too much > stuff in > > > >> > > > >>>>>>> the amount of RAM that you have. I guess it's the map and > reduce tasks > > > >> > > > >>>>>>> that eat all the free space? Why not lower their number? > > > >> > > > >>>>>>> > > > >> > > > >>>>>>> J-D > > > >> > > > >>>>>>> > > > >> > > > >>>>>>> On Wed, Jul 7, 2010 at 11:22 AM, Jamie Cockrill > > > >> > > > >>>>>>> <[email protected]> wrote: > > > >> > > > >>>>>>>> PS, I've now reset my MAX_FILESIZE back to the default. (from > the 1GB > > > >> > > > >>>>>>>> i raised it to). It caused me to run into a delightful > > > >> > > > >>>>>>>> 'YouAreDeadException' which looks very related to the Garbage > > > >> > > > >>>>>>>> collection issues on the Troubleshooting page, as my Zookeeper > session > > > >> > > > >>>>>>>> expired. > > > >> > > > >>>>>>>> > > > >> > > > >>>>>>>> Thanks > > > >> > > > >>>>>>>> > > > >> > > > >>>>>>>> Jamie > > > >> > > > >>>>>>>> > > > >> > > > >>>>>>>> > > > >> > > > >>>>>>>> > > > >> > > > >>>>>>>> On 7 July 2010 19:19, Jamie Cockrill > <[email protected]> wrote: > > > >> > > > >>>>>>>>> By overcommit, do you mean make my overcommit_ratio higher on > each box > > > >> > > > >>>>>>>>> (its at the default 50 at the moment)? What I'm noticing at > the moment > > > >> > > > >>>>>>>>> is that hadoop is taking up the vast majority of the memory > on the > > > >> > > > >>>>>>>>> boxes. > > > >> > > > >>>>>>>>> > > > >> > > > >>>>>>>>> I found this article: > > > >> > > > >>>>>>>>> http://blog.rapleaf.com/dev/2010/01/05/the-wrath-of-drwho-or- > unpredictable-hadoop-memory-usage/ > > > >> > > > >>>>>>>>> which Todd, it looks like you replied to. Does this sound > like a > > > >> > > > >>>>>>>>> similar problem? No worries if you can't remember, it was > back in > > > >> > > > >>>>>>>>> january! This article suggests reducing the amount of memory > allocated > > > >> > > > >>>>>>>>> to Hadoop at startup, how would I go about doing this? > > > >> > > > >>>>>>>>> > > > >> > > > >>>>>>>>> Thank you everyone for your patience so far. Sorry if this is > taking > > > >> > > > >>>>>>>>> up a lot of your time. > > > >> > > > >>>>>>>>> > > > >> > > > >>>>>>>>> Thanks, > > > >> > > > >>>>>>>>> > > > >> > > > >>>>>>>>> Jamie > > > >> > > > >>>>>>>>> > > > >> > > > >>>>>>>>> On 7 July 2010 19:03, Jean-Daniel Cryans > <[email protected]> wrote: > > > >> > > > >>>>>>>>>> swappinness at 0 is good, but also don't overcommit your > memory! > > > >> > > > >>>>>>>>>> > > > >> > > > >>>>>>>>>> J-D > > > >> > > > >>>>>>>>>> > > > >> > > > >>>>>>>>>> On Wed, Jul 7, 2010 at 10:53 AM, Jamie Cockrill > > > >> > > > >>>>>>>>>> <[email protected]> wrote: > > > >> > > > >>>>>>>>>>> I think you're right. > > > >> > > > >>>>>>>>>>> > > > >> > > > >>>>>>>>>>> Unfortunately the machines are on a separate network to > this laptop, > > > >> > > > >>>>>>>>>>> so I'm having to type everything across, apologies if it > doesn't > > > >> > > > >>>>>>>>>>> translate well... > > > >> > > > >>>>>>>>>>> > > > >> > > > >>>>>>>>>>> free -m gave: > > > >> > > > >>>>>>>>>>> > > > >> > > > >>>>>>>>>>> Mem Total Used Free > > > >> > > > >>>>>>>>>>> 7992 7939 53 > > > >> > > > >>>>>>>>>>> b/c 7877 114 > > > >> > > > >>>>>>>>>>> Swap: 23415 895 22519 > > > >> > > > >>>>>>>>>>> > > > >> > > > >>>>>>>>>>> I did this on another node that isn't being smashed at the > moment and > > > >> > > > >>>>>>>>>>> the numbers came out similar, but the buffers/cache free > was higher > > > >> > > > >>>>>>>>>>> > > > >> > > > >>>>>>>>>>> vmstat -20 is giving non-zero si and so's ranging between 3 > and just > > > >> > > > >>>>>>>>>>> short of 5000. > > > >> > > > >>>>>>>>>>> > > > >> > > > >>>>>>>>>>> That seems to be it I guess. Hadoop troubleshooting > suggests setting > > > >> > > > >>>>>>>>>>> swappiness to 0, is that just a case of changing the value > in > > > >> > > > >>>>>>>>>>> /proc/sys/vm/swappiness? > > > >> > > > >>>>>>>>>>> > > > >> > > > >>>>>>>>>>> thanks > > > >> > > > >>>>>>>>>>> > > > >> > > > >>>>>>>>>>> Jamie > > > >> > > > >>>>>>>>>>> > > > >> > > > >>>>>>>>>>> > > > >> > > > >>>>>>>>>>> > > > >> > > > >>>>>>>>>>> > > > >> > > > >>>>>>>>>>> On 7 July 2010 18:40, Todd Lipcon <[email protected]> > wrote: > > > >> > > > >>>>>>>>>>>> On Wed, Jul 7, 2010 at 10:32 AM, Jamie Cockrill > <[email protected]>wrote: > > > >> > > > >>>>>>>>>>>> > > > >> > > > >>>>>>>>>>>>> On the subject of GC and heap, I've left those as > defaults. I could > > > >> > > > >>>>>>>>>>>>> look at those if that's the next logical step? Would > there be > > > >> > > > >> anything > > > >> > > > >>>>>>>>>>>>> in any of the logs that I should look at? > > > >> > > > >>>>>>>>>>>>> > > > >> > > > >>>>>>>>>>>>> One thing I have noticed is that it does take an absolute > age to > > > > log > > > >> > > > >>>>>>>>>>>>> in to the DN/RS to restart the RS once it's fallen over, > in one > > > >> > > > >>>>>>>>>>>>> instance it took about 10 minutes. These are 8GB, 4 core > amd64 > > > > boxes > > > >> > > > >>>>>>>>>>>>> > > > >> > > > >>>>>>>>>>>>> > > > >> > > > >>>>>>>>>>>> That indicates swapping. Can you run "free -m" on the > node? > > > >> > > > >>>>>>>>>>>> > > > >> > > > >>>>>>>>>>>> Also let "vmstat 20" run while running your job and > observe the "si" > > > >> > > > >> and > > > >> > > > >>>>>>>>>>>> "so" columns. If those are nonzero, it indicates you're > swapping, > > > > and > > > >> > > > >> you've > > > >> > > > >>>>>>>>>>>> oversubscribed your RAM (very easy on 8G machines) > > > >> > > > >>>>>>>>>>>> > > > >> > > > >>>>>>>>>>>> -Todd > > > >> > > > >>>>>>>>>>>> > > > >> > > > >>>>>>>>>>>> > > > >> > > > >>>>>>>>>>>> > > > >> > > > >>>>>>>>>>>>> ta > > > >> > > > >>>>>>>>>>>>> > > > >> > > > >>>>>>>>>>>>> Jamie > > > >> > > > >>>>>>>>>>>>> > > > >> > > > >>>>>>>>>>>>> > > > >> > > > >>>>>>>>>>>>> > > > >> > > > >>>>>>>>>>>>> On 7 July 2010 18:30, Jamie Cockrill > <[email protected]> > > > >> > > > >> wrote: > > > >> > > > >>>>>>>>>>>>> > Bad news, it looks like my xcievers is set as it should > be, it's > > > >> > > > >> in > > > >> > > > >>>>>>>>>>>>> > the hdfs-site.xml and looking at the job.xml of one of > my jobs in > > > >> > > > >> the > > > >> > > > >>>>>>>>>>>>> > job-tracker, it's showing that property as set to 2047. > I've cat > > > > | > > > >> > > > >>>>>>>>>>>>> > grepped one of the datanode logs and although there > were a few in > > > >> > > > >>>>>>>>>>>>> > there, they were from a few months ago. I've upped my > > > > MAX_FILESIZE > > > >> > > > >> on > > > >> > > > >>>>>>>>>>>>> > my table to 1GB to see if that helps (not sure if it > will!). > > > >> > > > >>>>>>>>>>>>> > > > > >> > > > >>>>>>>>>>>>> > Thanks, > > > >> > > > >>>>>>>>>>>>> > > > > >> > > > >>>>>>>>>>>>> > Jamie > > > >> > > > >>>>>>>>>>>>> > > > > >> > > > >>>>>>>>>>>>> > On 7 July 2010 18:12, Jean-Daniel Cryans > <[email protected]> > > > >> > > > >> wrote: > > > >> > > > >>>>>>>>>>>>> >> xcievers exceptions will be in the datanodes' logs, > and your > > > >> > > > >> problem > > > >> > > > >>>>>>>>>>>>> >> totally looks like it. 0.20.5 will have the same issue > (since > > > >> > > > >> it's on > > > >> > > > >>>>>>>>>>>>> >> the HDFS side) > > > >> > > > >>>>>>>>>>>>> >> > > > >> > > > >>>>>>>>>>>>> >> J-D > > > >> > > > >>>>>>>>>>>>> >> > > > >> > > > >>>>>>>>>>>>> >> On Wed, Jul 7, 2010 at 10:08 AM, Jamie Cockrill > > > >> > > > >>>>>>>>>>>>> >> <[email protected]> wrote: > > > >> > > > >>>>>>>>>>>>> >>> Hi Todd & JD, > > > >> > > > >>>>>>>>>>>>> >>> > > > >> > > > >>>>>>>>>>>>> >>> Environment: > > > >> > > > >>>>>>>>>>>>> >>> All (hadoop and HBase) installed as of karmic-cdh3, > which > > > > means: > > > >> > > > >>>>>>>>>>>>> >>> Hadoop 0.20.2+228 > > > >> > > > >>>>>>>>>>>>> >>> HBase 0.89.20100621+17 > > > >> > > > >>>>>>>>>>>>> >>> Zookeeper 3.3.1+7 > > > >> > > > >>>>>>>>>>>>> >>> > > > >> > > > >>>>>>>>>>>>> >>> Unfortunately my whole cluster of regionservers have > now > > > >> > > > >> crashed, so I > > > >> > > > >>>>>>>>>>>>> >>> can't really say if it was swapping too much. There > is a DEBUG > > > >> > > > >>>>>>>>>>>>> >>> statement just before it crashes saying: > > > >> > > > >>>>>>>>>>>>> >>> > > > >> > > > >>>>>>>>>>>>> >>> org.apache.hadoop.hbase.regionserver.wal.HLog: > closing hlog > > > >> > > > >> writer in > > > >> > > > >>>>>>>>>>>>> >>> hdfs://<somewhere on my HDFS, in /hbase> > > > >> > > > >>>>>>>>>>>>> >>> > > > >> > > > >>>>>>>>>>>>> >>> What follows is: > > > >> > > > >>>>>>>>>>>>> >>> > > > >> > > > >>>>>>>>>>>>> >>> WARN org.apache.hadoop.hdfs.DFSClient: DataStreamer > Exception: > > > >> > > > >>>>>>>>>>>>> >>> org.apache.hadoop.ipc.RemoteException: > > > >> > > > >>>>>>>>>>>>> >>> > org.apache.hadoop.hdfs.server.namenode.LeaseExpiredException: > > > > No > > > >> > > > >> lease > > > >> > > > >>>>>>>>>>>>> >>> on <file location as above> File does not exist. > Holder > > > >> > > > >>>>>>>>>>>>> >>> DFSClient_-11113603 does not have any open files > > > >> > > > >>>>>>>>>>>>> >>> > > > >> > > > >>>>>>>>>>>>> >>> It then seems to try and do some error recovery > (Error Recovery > > > >> > > > >> for > > > >> > > > >>>>>>>>>>>>> >>> block null bad datanode[0] nodes == null), fails > (Could not get > > > >> > > > >> block > > > >> > > > >>>>>>>>>>>>> >>> locations. Source file "<hbase file as before>" - > Aborting). > > > >> > > > >> There is > > > >> > > > >>>>>>>>>>>>> >>> then an ERROR org.apache...HRegionServer: Close and > delete > > > >> > > > >> failed. > > > >> > > > >>>>>>>>>>>>> >>> There is then a similar LeaseExpiredException as > above. > > > >> > > > >>>>>>>>>>>>> >>> > > > >> > > > >>>>>>>>>>>>> >>> There are then a couple of messages from > HRegionServer saying > > > >> > > > >> that > > > >> > > > >>>>>>>>>>>>> >>> it's notifying master of its shutdown and stopping > itself. The > > > >> > > > >>>>>>>>>>>>> >>> shutdown hook then fires and the RemoteException and > > > >> > > > >>>>>>>>>>>>> >>> LeaseExpiredExceptions are printed again. > > > >> > > > >>>>>>>>>>>>> >>> > > > >> > > > >>>>>>>>>>>>> >>> ulimit is set to 65000 (it's in the regionserver log, > printed > > > > as > > > >> > > > >> I > > > >> > > > >>>>>>>>>>>>> >>> restarted the regionserver), however I haven't got > the xceivers > > > >> > > > >> set > > > >> > > > >>>>>>>>>>>>> >>> anywhere. I'll give that a go. It does seem very odd > as I did > > > >> > > > >> have a > > > >> > > > >>>>>>>>>>>>> >>> few of them fall over one at a time with a few early > loads, but > > > >> > > > >> that > > > >> > > > >>>>>>>>>>>>> >>> seemed to be because the regions weren't splitting > properly, so > > > >> > > > >> all > > > >> > > > >>>>>>>>>>>>> >>> the traffic was going to one node and it was being > overwhelmed. > > > >> > > > >> Once I > > > >> > > > >>>>>>>>>>>>> >>> throttled it, after one load it a region split seemed > to get > > > >> > > > >>>>>>>>>>>>> >>> triggered, which flung regions all over, which made > subsequent > > > >> > > > >> loads > > > >> > > > >>>>>>>>>>>>> >>> much more distributed. However, perhaps the time-bomb > was > > > >> > > > >> ticking... > > > >> > > > >>>>>>>>>>>>> >>> I'll have a go at specifying the xcievers property. > I'm pretty > > > >> > > > >>>>>>>>>>>>> >>> certain i've got everything else covered, except the > patches as > > > >> > > > >>>>>>>>>>>>> >>> referenced in the JIRA. > > > >> > > > >>>>>>>>>>>>> >>> > > > >> > > > >>>>>>>>>>>>> >>> I just grepped some of the log files and didn't get > an explicit > > > >> > > > >>>>>>>>>>>>> >>> exception with 'xciever' in it. > > > >> > > > >>>>>>>>>>>>> >>> > > > >> > > > >>>>>>>>>>>>> >>> I am considering downgrading(?) to 0.20.5, however > because > > > >> > > > >> everything > > > >> > > > >>>>>>>>>>>>> >>> is installed as per karmic-cdh3, I'm a bit reluctant > to do so > > > > as > > > >> > > > >>>>>>>>>>>>> >>> presumably Cloudera has tested each of these versions > against > > > >> > > > >> each > > > >> > > > >>>>>>>>>>>>> >>> other? And I don't really want to introduce further > versioning > > > >> > > > >> issues. > > > >> > > > >>>>>>>>>>>>> >>> > > > >> > > > >>>>>>>>>>>>> >>> Thanks, > > > >> > > > >>>>>>>>>>>>> >>> > > > >> > > > >>>>>>>>>>>>> >>> Jamie > > > >> > > > >>>>>>>>>>>>> >>> > > > >> > > > >>>>>>>>>>>>> >>> > > > >> > > > >>>>>>>>>>>>> >>> On 7 July 2010 17:30, Jean-Daniel Cryans > <[email protected]> > > > >> > > > >> wrote: > > > >> > > > >>>>>>>>>>>>> >>>> Jamie, > > > >> > > > >>>>>>>>>>>>> >>>> > > > >> > > > >>>>>>>>>>>>> >>>> Does your configuration meets the requirements? > > > >> > > > >>>>>>>>>>>>> >>>> > > > >> > > > >>>>>>>>>>>>> http://hbase.apache.org/docs/r0.20.5/api/overview- > summary.html#requirements > > > >> > > > >>>>>>>>>>>>> >>>> > > > >> > > > >>>>>>>>>>>>> >>>> ulimit and xcievers, if not set, are usually time > bombs that > > > >> > > > >> blow off > > > >> > > > >>>>>>>>>>>>> when > > > >> > > > >>>>>>>>>>>>> >>>> the cluster is under load. > > > >> > > > >>>>>>>>>>>>> >>>> > > > >> > > > >>>>>>>>>>>>> >>>> J-D > > > >> > > > >>>>>>>>>>>>> >>>> > > > >> > > > >>>>>>>>>>>>> >>>> On Wed, Jul 7, 2010 at 9:11 AM, Jamie Cockrill < > > > >> > > > >>>>>>>>>>>>> [email protected]>wrote: > > > >> > > > >>>>>>>>>>>>> >>>> > > > >> > > > >>>>>>>>>>>>> >>>>> Dear all, > > > >> > > > >>>>>>>>>>>>> >>>>> > > > >> > > > >>>>>>>>>>>>> >>>>> My current HBase/Hadoop architecture has HBase > region servers > > > >> > > > >> on the > > > >> > > > >>>>>>>>>>>>> >>>>> same physical boxes as the HDFS data-nodes. I'm > getting an > > > >> > > > >> awful lot > > > >> > > > >>>>>>>>>>>>> >>>>> of region server crashes. The last thing that > happens appears > > > >> > > > >> to be a > > > >> > > > >>>>>>>>>>>>> >>>>> DroppedSnapshot Exception, caused by an > IOException: could > > > > not > > > >> > > > >>>>>>>>>>>>> >>>>> complete write to file <file on HDFS>. I am running > it under > > > >> > > > >> load, > > > >> > > > >>>>>>>>>>>>> how > > > >> > > > >>>>>>>>>>>>> >>>>> heavy that is I'm not sure how that is quantified, > but I'm > > > >> > > > >> guessing > > > >> > > > >>>>>>>>>>>>> it > > > >> > > > >>>>>>>>>>>>> >>>>> is a load issue. > > > >> > > > >>>>>>>>>>>>> >>>>> > > > >> > > > >>>>>>>>>>>>> >>>>> Is it common practice to put region servers on > data-nodes? Is > > > >> > > > >> it > > > >> > > > >>>>>>>>>>>>> >>>>> common to see region server crashes when either the > HDFS or > > > >> > > > >> region > > > >> > > > >>>>>>>>>>>>> >>>>> server (or both) is under heavy load? I'm guessing > that is > > > > the > > > >> > > > >> case > > > >> > > > >>>>>>>>>>>>> as > > > >> > > > >>>>>>>>>>>>> >>>>> I've seen a few similar posts. I've not got a great > deal of > > > >> > > > >> capacity > > > >> > > > >>>>>>>>>>>>> >>>>> to be separating region servers from HDFS data > nodes, but it > > > >> > > > >> might be > > > >> > > > >>>>>>>>>>>>> >>>>> an argument I could make. > > > >> > > > >>>>>>>>>>>>> >>>>> > > > >> > > > >>>>>>>>>>>>> >>>>> Thanks > > > >> > > > >>>>>>>>>>>>> >>>>> > > > >> > > > >>>>>>>>>>>>> >>>>> Jamie > > > >> > > > >>>>>>>>>>>>> >>>>> > > > >> > > > >>>>>>>>>>>>> >>>> > > > >> > > > >>>>>>>>>>>>> >>> > > > >> > > > >>>>>>>>>>>>> >> > > > >> > > > >>>>>>>>>>>>> > > > > >> > > > >>>>>>>>>>>>> > > > >> > > > >>>>>>>>>>>> > > > >> > > > >>>>>>>>>>>> > > > >> > > > >>>>>>>>>>>> > > > >> > > > >>>>>>>>>>>> -- > > > >> > > > >>>>>>>>>>>> Todd Lipcon > > > >> > > > >>>>>>>>>>>> Software Engineer, Cloudera > > > >> > > > >>>>>>>>>>>> > > > >> > > > >>>>>>>>>>> > > > >> > > > >>>>>>>>>> > > > >> > > > >>>>>>>>> > > > >> > > > >>>>>>>> > > > >> > > > >>>>>>> > > > >> > > > >>>>>> > > > >> > > > >>>>> > > > >> > > > >>>> > > > >> > > > >>> > > > >> > > > >> > > > >> > > > >> > > > > > > > >
