zCeph: Achieving High Performance On Storage System Using Small Zoned ZNS SSD

Abstract

ZNS SSDs (Zoned Namespace SSD) are block devices that provide stable performance and low price by forcing sequential writes, however their users have to pay the price to guarantee strong write order. In addition, to get the best performance from small zoned ZNS SSDs that give the users control over device-internal parallel elements, the users need to utilize the SSDs in detail. Due to these overheads, Ceph, one of the distributed storage systems, has up to 69% lower performance when using ZNS SSDs compared to using legacy SSD. In this paper, we present zCeph which solves the problems that occur when using small zoned ZNS SSD in storage systems. We implemented zCeph based on legacy Ceph and evaluated it using synthesized and real-world workloads, showing that the performance improved by up to 4.1x and 7x, respectively, compared to the legacy Ceph using ZNS SSD.