Inline Regards, Dhaval
________________________________ From: Upendra Yadav <[email protected]> To: [email protected] Sent: Tuesday, 25 February 2014 1:00 PM Subject: Need some information over WAL I have also doubt over WAL(write ahead log). In hdfs we can write a new file or we can append to old file. Is that correct : 1. WAL only logs operations not its data... just like disk journaling(ext4) - No WAL is a log of all new data, not just the operations 2. In case of Region Server failure... WAL replay will depends on Client to get each operation's data that yet not committed/flushed to hdfs. - No client will not generally know of a region server failure. It gets the data from the WAL and replays it. The client may not even exist when a region server crashes 3. Hbase uses append operation in hdfs to store/log WAL. - Yes Thanks...
