Is Synchronous Replication Enough?

By Zerto, on 29 May, 2013

This is a guest post by Joshua Stenhouse, Zerto’s UK-based Solutions Engineer.

Is Synchronous Replication enough? Application consistency and replication to a 3rd site are the keys to true disaster recovery.

Failover to either crash or application consistent points in time using ZertoOne misconception I often come across is that synchronous replication is the holy grail of ensuring zero data loss. Let me be clear; synchronous replication is not application consistent and you definitely can lose data! To explain; just because a change is immediately written in both sites does not mean that all of the transactions have been committed from memory. All replication solutions are bound by the same rules when it comes to application consistency.

The irony of this is that any customer who has such valuable data to warrant the expense, distance limitations and complexity of a synchronous replication solution, often only considers their last application consistent point in time as their real Recovery Point Objective (RPO). Otherwise they cannot be sure their data is 100% consistent.

With Zerto we are replicating Virtual Machines from the hypervisor to remove the limitations and complexity of synchronous replication solutions. Zerto replicates the disk writes as they occur within seconds to the recovery site. Zerto is the only replication solution that gives you the ability to failover to any crash or application consistent point in time within the last 5 days, which synchronous replication cannot do. Application consistent points in time can be scheduled on a per application basis, on individual schedules, giving the ability to take them as frequently as possible without impacting production.

Using synchronous replication, recovering to an application consistent point in time requires recovery from backup or snapshot which can be both complex and slow.

If you already have a synchronous replication solution installed I’m certainly not recommending to rip out and replace such a significant investment. However,  combining this solution with Zerto to enable true 3rd site replication gives the ultimate datacentre configuration of both high availability and disaster recovery.

Zerto can be installed and running in just 1 hour, replicating with an RPO of seconds over a standard IP link and is completely storage agnostic. Try that with any other enterprise replication solution! If you are interested in arranging a trial installation please click here.

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