NIC NVRAM Write Packet Log for Distributed Storage Latency
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Solution Overview
Problem
Distributed object storage systems face write latency due to the 'write-twice penalty' caused by the journal mechanism, which requires at least two I/O requests for journaling and final data disk writes, resulting in increased processing time.
Innovation Solution
Implementing a network interface controller (NIC) with non-volatile random access memory (NVRAM) to log write packets, allowing for a write-ahead log that reduces or eliminates the write-twice penalty by storing write packets in NVRAM and replaying them in case of a system crash, thus releasing the server from journal-related work.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a journal mechanism is used to ensure data consistency, then reliability is improved, but write latency increases due to the write-twice penalty
Solution Approach 1:
The patent implements a write-ahead log (WAL) mechanism where write operations are first logged to NVRAM before being committed to the journal. This preliminary action in NVRAM (which has much faster write speeds than journal storage) allows the system to acknowledge writes quickly while maintaining data consistency through the subsequent journal commit, thereby reducing write latency while preserving reliability
Solution Approach 2:
The patent introduces NVRAM as an intermediary layer between the fast network interface and the slower journal storage. This intermediary buffer allows write operations to be temporarily stored in NVRAM, decoupling the fast write path from the slower journal commit process, thus eliminating the write-twice penalty without sacrificing data consistency
2Reliability
If two I/O requests are required for journaling and final data disk writes, then data integrity is ensured, but processing time increases
Solution Approach 1:
The system performs preliminary write operations to NVRAM before final journal commit. This preliminary action allows the majority of write processing to complete in the fast NVRAM medium, with only a single slower journal commit operation required afterward, thereby improving processing speed while maintaining data integrity through the two-phase commit mechanism
Solution Approach 2:
The patent segments the write operation into two distinct phases: (1) fast write to NVRAM which can be acknowledged immediately, and (2) slower journal commit which ensures durability. This segmentation allows the system to provide fast path performance for most operations while maintaining integrity through the eventual journal commit, improving overall productivity
3Reliability
If the server performs journal-related work, then data consistency is maintained, but the server workload increases
Solution Approach 1:
The patent extracts the journaling functionality from the server and relocates it to the NIC's NVRAM. The NIC autonomously manages the write-ahead log in its local NVRAM, freeing the server from journal-related processing workloads. The server only needs to perform final commit operations, significantly reducing server complexity and workload while maintaining data consistency through the distributed journaling mechanism
Data Source
AI summary
Embodiments of the present disclosure provide devices, techniques, and configurations for network interface controllers (NICs) that log write packets received from a network in non-volatile random access memory (NVRAM). In one embodiment, a NIC includes a network interface to couple a host of the NIC to a network, a NVRAM, and a controller coupled with the network interface and the NVRAM, where the controller is to log write packets received at the network interface from the network in the NVRAM. Other embodiments may be described and/or claimed.