RDMA Verbs Extensions for Persistency and Consistency

Standard block/file storage protocols assume that the data will be bounced through intermediate buffer in memory while writing into the remote disk, this assumption came from two interface characteristics of the underlying storage: 1. Storage latency is higher with respect to network latency 2. Storage is not byte addressable, accessing the storage requires asynchronous command/completion interface. Persistent memory (PMEM) / storage class memory (SCM) breaks the assumptions above, PMEM devices expose byte addressable storage that can be accessible through RDMA network and have the latency characteristics that fits the latency of high speed RDMA networks, sub microsecond latency. In this talk I will discuss the current IB/RoCE VERBs semantics for accessing memory through RDMA and the reliability model within them, I will share the challenges of using the VERBs reliability for accessing persistent memory and share the initial thought about the reliability and consistency extensions work we are doing in IBTA in order to meet the reliability requirement of storage access.

Learning Objectives

PMEM
RDMA
Reliability
File system
PMEM.IO