Thanks, for the suggestions. Will do instrumentation based on JMX. Regards, Yun
On Nov 12, 2012, at 12:59 AM, Stack <[email protected]> wrote: > On Sat, Nov 10, 2012 at 7:03 AM, yun peng <[email protected]> wrote: >> Hi, I want to profile the # of disk access (both random and sequential) >> issued from HBase (into HDFS). For disk reads, I have tried use >> blockCacheMissCount, which seems working. But is it the correct way for >> reads (I can't confirmed it from HBase documents)? >> > > That should give you a coarse measure. If you need better than that > you may need to instrument the code some to dump more detailed metric > on whether random or sequential access. Beware that hdfs may be > reading from file system cache avoiding disk altogether on some reads. > >> For disk writes, I can't find any metrics in HBase. How should one get disk >> writes in HBase? >> > > We write when we append to the WAL and when we flush hfiles. If you > need actual disk accesses, you'll probably need to add some extra > emissions in the code; per WAL edit and then as we flush. Again, hdfs > flush/sync usually means flush from hbase to hdfs; more specifically > to datanode memory and not necessarily to disk (at least currently). > > St.Ack
