Thanks for your suggestion. As our insertion is daily, that's to insert lots of records at fixed time, can we just call HBaseAdmin.flush to avoid loss? I have done some experiments and find it works. I wonder if it will cause some other problem?
2009/8/14 Ryan Rawson <[email protected]> > HDFS doesnt allow you to read partially written files, it reports the > size as 0 until the file is properly closed, under a crash scenario > you are in trouble. > > The best options right now are to: > - dont let hbase crash (not as crazy as this sounds) > - consider experimenting with some newer hdfs stuff > - wait for hadoop 0.21 > > in the mean time, you will suffer loss if hbase regionservers crash. > That is a crash as in hard crash, controlled shutdowns flush and you > dont lose data then. > > sorry for the confusion! > -ryan > > On Thu, Aug 13, 2009 at 10:56 PM, Chen Xinli<[email protected]> wrote: > > For the Hlog, I find an interesting problem. I set the > > optionallogflushinterval to 10000, that's 10 seconds; but it flushes with > > the interval of 1 hour. > > > > After the hlog file generated, I stop hdfs and then kill hmaster and > > regionservers; then I start all again, the hmaster doesn't restore > records > > from hlog, that's the record lost again. Is there something wrong? > > > > > > 2009/8/14 Chen Xinli <[email protected]> > > > >> Thanks Daniel. As you said the latest version has done much to avoid > data > >> loss, would you pls give some example? > >> > >> I read the conf file and api, and find some functions related: > >> 1. in hbase-default.xml, "hbase.regionserver.optionallogflushinterval" > >> described as "Sync the HLog to the HDFS after this interval if it has > not > >> accumulated enough entries to trigger a sync". I issued one update to my > >> table, but there's no hlog files after the specifed interval. > >> This setting doesn't work, or I make a misunderstanding? > >> > >> 2. HbaseAdmin.flush(tableOrRegionName). It seems that this function > flush > >> the memcache to HStorefile. Should I call this function to avoid data > loss > >> after several thousand updation? > >> > >> 3. In Htable, there is also a function flushCommits. Where does it flush > >> to? memcache or hdfs? > >> > >> Actually we have a crawler, and want to store webpages(about 1 billion) > in > >> hbase. What shall we do to avoid data loss? Any suggestion is > appreciated. > >> > >> By the way, we use hadoop 0.19.1 + hbase 0.19.3 > >> Thanks > >> > >> 2009/8/6 Jean-Daniel Cryans <[email protected]> > >> > >> Chen, > >>> > >>> The main problem is that appends are not supported in HDFS, HBase > >>> simply cannot sync its logs to it. But, we did some work to make that > >>> story better. The latest revision in the 0.19 branch and 0.20 RC1 both > >>> solve much of the data loss problem but it won't be near perfect until > >>> we have appends (supposed to be available in 0.21). > >>> > >>> J-D > >>> > >>> On Thu, Aug 6, 2009 at 12:45 AM, Chen Xinli<[email protected]> > wrote: > >>> > Hi, > >>> > > >>> > I'm using hbase 0.19.3 on a cluster with 30 machines to store web > data. > >>> > We got a poweroff days before and I found much web data lost. I have > >>> > searched google, and find it's a meta flush problem. > >>> > > >>> > I know there is much performance improvement in 0.20.0; Is the data > lost > >>> > problem handled in the new version? > >>> > > >>> > -- > >>> > Best Regards, > >>> > Chen Xinli > >>> > > >>> > >> > >> > >> > >> -- > >> Best Regards, > >> Chen Xinli > >> > > > > > > > > -- > > Best Regards, > > Chen Xinli > > > -- Best Regards, Chen Xinli
