Evolving Ext4 for Shingled Disks

Multi-terabyte hard disks today use Shingled Magnetic Recording (SMR), a technique that increases capacity at the expense of more costly random writes. We introduce ext4-lazy, a small change to the popular Linux ext4 file system that eliminates a major source of random writes—the metadata writeback—significantly improving performance on SMR disks in general, as well as on conventional disks for metadata-heavy workloads in particular. In this article, we briefly explain why SMR disks suffer under random writes and how ext4-lazy helps.