1.1. DRX
Data Replication Xcelerator (DRX) is a replication acceleration solution that maximizes replication performance in long-distance(DR) replication with DRBD.
The replication provided by DRBD operates synchronously or asynchronously depending on the configuration environment and purpose. A synchronization method is commonly used in local HA mirror configurations to ensure full target coherency when source node failures occur, but it impacts local I/O performance due to the nature of synchronous implementation. The asynchronous method is suitable for long-distance replication. Although the RPO is somewhat lower than the synchronous method, the replication performance and the local I/O response latency are good, so most long-distance replication is assumed to operate asynchronously. However, even if asynchronous replication does not impact local operations in architectures, the following environmental problems that compromise replication performance in WAN environments will inevitably lead to performance degradation in replication throughput.
- Because the WAN transmission bandwidth is significantly lower than the local I/O replication bandwidth, replication data throughput is degraded and replication latency degradation occurs.
- Replication transfer protocol (TCP/IP) can cause delays due to data retransmission because transmission delays and packet losses may occur in the WAN interval.
If these issues are not resolved and asynchronous replication is run in the WAN environment, replication will not fundamentally achieve the goal of minimizing the RPO, and as a result, it will not be able to guarantee the data integrity of the replication target. DRX provides a solution to these problems.
DRX is a kind of proxy that directly integrates with DRBD to accommodate DRBD replicated data as a buffer in DRX, and provides optimized transmission for data transmission over the WAN interval through buffering and compression.
DRX implements a sufficient level of data buffering to perform replication in a low transmission band, thereby buffering replicated I/O load, realizing data de-duplication through data compression, and transmitting data to be processed by the TCP protocol Minimizes costs and shortens the physical replication transfer time over the WAN. Compression can have compression delays depending on the compress level, but it can offset the cost of these delays because you can get a significant reduction in physical data transfer time, and you get maximum compression performance when using dedicated compression boards. This is a traditional WAN optimization approach and DRX implements multi-channel simultaneous replication acceleration with high-level compression.
DRX provides high-performance, real-time data encryption (AES 128-bit) at the same time with this compression, providing an effective solution to problems such as data leaks that can occur when important data of a company goes through the WAN transmission interval.
The following figure shows how DRX and DRBD work together.
1.2. 네트워크 구성
DRX는 기본적으로 로컬 DRX와 원격 DRX의 2 프록시 구조로 구축하며 버퍼링, 압축, 암호화의 기능은 로컬-원격 DRX 구간(WAN 구간)내에서 구현되어 복제 환경에 투명하게 기능 합니다. 이러한 투명성은 복제 환경과의 연동 시 유연함을 제공하여 다음 그림과 같이 다양하게 구성할 수 있는 뛰어난 확장성을 제공합니다.
- 로컬 구성 방식: 기 구축환경에 DRBD와 DRX를 모두 설치하여 운영할 수 있습니다.
- 전용 구성 방식: DRX 전용머신을 통해 다 채널 DRBD 리소스를 운영할 수 있습니다.
- 복합 구성 방식: 로컬설치 방식과 전용구성 설치 방식을 혼합하여 운영할 수 있습니다.