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. Network configuration
DRX is basically constructed with two proxy structures of local DRX and remote DRX. The functions of buffering, compression, and encryption are implemented within the local-remote DRX interval (WAN interval), and functions transparently to the replication environment. This transparency provides flexibility in interworking with the replication environment and provides excellent scalability that can be configured as shown in the following figure.
- Local configuration method: Both DRBD and DRX can be installed and operated in a pre-built environment.
- Dedicated configuration method: You can operate multi-channel DRBD resources through a dedicated DRX machine.
- Composite configuration method: You can mix the local installation method and the dedicated configuration method.