User's Guide for DRX 1.2 or later.

Necessity

In real-world WAN environments, real-time replication data transfer is hindered by the following issues

The transmission bandwidth across the WAN is very low compared to the local I/O replication band, which reduces data throughput and causes replication delays.

Replication transport protocols (TCP/IP) are typically subject to transmission delays and packet losses across the WAN, causing delays in data retransmission.
If WAN asynchronous replication is operated without resolving these issues, severe replication delays are unavoidable, and it becomes impossible to maintain the replication state if replication delays and out-of-sync conditions are repeated.

DRX performs the function of buffering the replication I/O load by implementing a sufficient level of data buffering to perform replication in low transmission bands. It also implements real-time data deduplication through data compression to minimize the data transmission cost that the TCP protocol needs to handle and shorten the physical replication transmission time along the WAN section. This is a traditional WAN optimization approach, and in addition, it implements compressed, encrypted (AES 128 bit) real-time transmission in multichannel to achieve optimal multichannel replication acceleration.

Replication uses DRX buffering to accomplish this, rather than performing buffering directly as data is transferred. Because performing large amounts of buffering at the kernel layer can have a systemic impact, it makes sense to offload buffering to a separate proxy(DRX).

The following figure shows the interworking between DRX and replication.

Network Configuration

By default, DRX is deployed in a two-proxy structure: a local DRX and a remote DRX. It implements the functions of buffering, compression, and encryption within the 2-proxy section, so it functions transparently to the replication environment. This transparency provides flexibility in interfacing with the replication environment, providing excellent scalability that can be configured in various ways as shown in the following figure.

Local configuration: Install and operate both replication and DRX in your production environment.
Dedicated: Operate with multi-channel replication via a separate DRX-dedicated machine.
Mixed configuration: Operate a mix of local and dedicated.

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