Okay, good to know but not sure how your response is related to what I asked.
On Tue, Nov 5, 2013 at 1:08 AM, Haosong Huang <[email protected]> wrote: > An os fsync() call will spent nearly 10ms because of the harddisk iops > neckbottle. A hsync() would become two os fsync(). One for checksum file > and theother for block file. If you use SSD disk, you could try use fsync() > instead of flush() and mount file system without writebarrier. > 2013-11-5 下午1:12于 "Himanshu Vashishtha" <[email protected]>写道： > > > Looking at ProtobufLogWriter class, it looks like the call to flush() in > > the sync method is a noop. > > > > > > > https://github.com/apache/hbase/blob/trunk/hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/wal/ProtobufLogWriter.java#L134 > > > > The underlying output stream is DFSOutputStream, which doesn't implement > > flush(). > > > > And, it calls sync() anyway, which ensures the data is written to DN's > > (cache). > > > > Previously with SequenceFile$Writer, it writes data to the outputstream > > (using Writables#write), and invoke sync/hflush. > > > > > https://github.com/apache/hadoop-common/blob/trunk/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/io/SequenceFile.java#L1314 > > > > Is there a reason we have this call here? Please let me know if I miss > any > > context. > > > > Thanks, > > Himanshu > > >
