Thanks Jon, Just for parallel log splitting. I got it.
Yifeng On Dec 25, 2011, at 12:39 AM, Jonathan Hsieh wrote: > Yifeng, > > HLog splitting is used to when shutting down a region server or to recover > log edits after a region server goes down uncleanly. > > Prior to 0.92, if many region servers go down uncleanly (maybe hdfs went > away under hbase), only a single process would do all log splitting in to > recover. If you have a lot of nodes, each has a hlog to split this can > take a long time (100 nodes = 100x the time). If you have many nodes going > down uncleanly you could manually use the HLog --split mechanism you > describe to split all the logs in parallel on many machines before > restarting hbase. > > As of 0.92, this hlog splitting is automatically distributed -- the feature > is called distributed log splitting. This farms work out the the nodes and > should significantly speedup up recovery in these scenarios. > > Jon. > > On Fri, Dec 23, 2011 at 6:59 PM, Yifeng Jiang <uprushwo...@gmail.com> wrote: > >> Hi, >> >> As mentioned in HBase Book, we can force a manual hlog splitting by: >> hbase org.apache.hadoop.hbase.regionserver.wal.HLog --split hdfs:// >> example.org:8020/hbase/.logs/example.org,60020,1283516293161/ >> >> What's the use case of this manual splitting? >> If RS is crashed, the hlog splitting will be triggered by master >> automatically. >> While, force a hlog splitting shuts down the RS if the RS is online. >> >> Thanks, >> Yifeng > > > > > -- > // Jonathan Hsieh (shay) > // Software Engineer, Cloudera > // j...@cloudera.com
