Short answer is "yes you can still lose data". It's about HDFS and HDFS-265 will solve this. Similar question was in the list a couple of days ago. Here's Ryan's answer. http://mail-archives.apache.org/mod_mbox/hadoop-hbase-user/200911.mbox/browser
On Mon, Nov 30, 2009 at 00:18, JQ Hadoop <[email protected]> wrote: > I have a question regarding the durability of HBase. After I have put > a record to HBase and have received a confirmation of the put from the > region server (assuming both autoFlush and writeToWAL are set to > true), can I be sure that my record will be there no matter what? I've > checked the code and found that the region server will first append a > log record to WAL (a SequenceFile) and then may call the sync() > function; however, it appears to me that this does not guarantee the > log record is in HDFS even if the sync() function is called. That is > to say, in case of RegionServer crash, the records put into HBase may > be lost; am I missing anything? > > Thanks, > -JQ >
