The accelerated writes feature in the HDInsight HBase cluster attaches a Premium SSD managed disk to every region server (worker node). Write ahead logs are configured to be written to Hadoop Distributed File System (HDFS) mounted on premium managed disks instead of standard Azure page blobs. Premium managed disks are SSD-based and offer excellent I/O performance with fault tolerance. Using premium managed disks for WALs allows us to separate write ahead log storage from Apache HBase data storage.
Source: Microsoft Azure – aggiornamenti