Sybase Adaptive Server vs Microsoft SQL Server High Availability and Disaster Recovery Solutions.

I have been Administering, Maintaining and Mentoring both Sybase Adaptive Server and Microsoft SQL Server for the past decade with Sybase is my primary skillset but slowly transforming into MS SQL Server as Primary due to the requirements in the Projects.

It is very difficult to make the comparison between SQL Server and Sybase ASE to identify which is the better product as both are siblings.

In a Quick nutshell:

•        1984 - Sybase founded and creates first RDBMS designed for online transactions.

•        1990 - Sybase entered into a technology sharing agreement with Microsoft which resulted in Microsoft marketing its own SQL Server. Microsoft releases SQL Server 1.1 for OS/2 with the engine of Sybase SQL Server.

•        1993 – SQL Server 4.2 for NT was released with Microsoft taking more control.

•        1994 – Sybase and Microsoft split ways and launched their own products but with same architecture and features.

•        1995 – SQL Server 6.0 is released; the first version without Sybase Support.

Over the past 2 decades, Microsoft has facilitated multiple features, tools and utilities for the ease of access and maintenance and administering compared to Sybase which provided Sybase central only. From a DBA standpoint MS SQL Server is easier to configure and maintain with its GUI tools but with sound scripting knowledge and right configuration Sybase is still robust. The performance of your databases depends rather from the experience of the database developers and database administrator than from the Product. You can use both of these RDBMS to build stable and efficient system. 

Microsoft SQL Server and Sybase ASE have a common architecture because, until version 4.2, Microsoft simply licensed Sybase's database server software. So these products had one kernel. After version 4.2, these products have diverged. Microsoft has produced versions 6.0, 6.5, 7.0, 2000, 2005, 2008 and 2012 of Microsoft SQL Server, while Sybase has produced versions 4.8, 4.9, System 10 and System 11 of Sybase SQL Server and versions 11.5, 11.9, 12, 12.5, 15 and 15.7 of Sybase Adaptive Server Enterprise.

High Availability and Disaster Recovery Concepts. 

When we compare the HA nd DR features till the year 2010 i.e. SQL Server 2008 and Sybase ASE 15, I found setup and configuration of Replication is easier in SQL Server due to its GUI based tools, but Sybase has clearly an edge with the features and availabiity.

•        Major advantage of Sybase replication is the Secondary replica can be used for the Reporting purpose for all kinds of Replication.

•        Fine tuning the Replication process and Trouble shooting is easier.

•        Database level Replication to multiple replicas can be setup easily.

You can make the best selection of a database technology for a high availability and disaster recovery solution when all stakeholders have a shared understanding of the related business drivers, challenges, and objectives of planning, managing, and measuring RTO and RPO objectives. But, recent times and especially, I was pleased to see the path-breaking new feature provided in SQL Server 2012 which combines all the pros and features of HA and DR called AlwaysOn Availability Groups. It's really an edge over all the available HA/DR options. As per the requirements in the recent Projects, I have set up multiple times the AlwaysOn Availability Groups and could see tangible improvements in the Databases Availability, Performance and ease of Maintenance. 

I have not considered SAP ASE 16 or MS SQL 2014.

For a given software application or service, high availability is ultimately measured in terms of the end user’s experience and expectations. The principal goal of a high availability solution is to minimize or mitigate the impact of downtime. A sound strategy for this optimally balances business processes and Service Level Agreements (SLAs) with technical capabilities and infrastructure costs.

The resulting value is often expressed by industry in terms of the number of 9’s that the solution provides; meant to convey an annual number of minutes of possible uptime, or conversely, minutes of downtime.

Number of 9’s	Availability Percentage	Total Annual Downtime
2	99%	3 days, 15 hours
3	99.9%	8 hours, 45 minutes
4	99.99%	52 minutes, 34 seconds
5	99.999%	5 minutes, 15 seconds

Data redundancy is a key component of a high availability database solution. Transactional activity on your primary SQL Server instance is synchronously or asynchronously applied to one or more secondary instances. When an outage occurs, transactions that were in flight may be rolled back, or they may be lost on the secondary instances due to delays in data propagation.

•        Avoiding downtime. Outage recovery costs are avoided all together if an outage doesn’t occur in the first place. Investments include the cost of fault-tolerant and redundant hardware or infrastructure, distributing workloads across isolated points of failure, and planned downtime for preventive maintenance.

•        Automating recovery. If a system failure occurs, you can greatly mitigate the impact of downtime on the customer experience through automatic and transparent recovery.

•        Resource utilization. Secondary or standby infrastructure can sit idle, awaiting an outage. It also can be leveraged for read-only workloads, or to improve overall system performance by distributing workloads across all available hardware.

SQL Server AlwaysOn

AlwaysOn is a new integrated, flexible, cost-efficient high availability and disaster recovery solution. It can provide data and hardware redundancy within and across data centers, and improves application failover time to increase the availability of your mission-critical applications. AlwaysOn provides flexibility in configuration and enables reuse of existing hardware investments.

An AlwaysOn solution can leverage two major SQL Server 2012 features for configuring availability at both the database and the instance level:

•        AlwaysOn Availability Groups, new in SQL Server 2012, greatly enhance the capabilities of database mirroring and helps ensure availability of application databases, and they enable zero data loss through log-based data movement for data protection without shared disks.

Availability groups provide an integrated set of options including automatic and manual failover of a logical group of databases, support for up to four secondary replicas, fast application failover, and automatic page repair.

•        AlwaysOn Failover Cluster Instances (FCIs) enhance the SQL Server failover clustering feature and support multisite clustering across subnets, which enables cross-data-center failover of SQL Server instances. Faster and more predictable instance failover is another key benefit that enables faster application recovery.

Significantly Reduce Planned Downtime

The key reason for application downtime in any organization is planned downtime caused by operating system patching, hardware maintenance, and so on. This can constitute almost 80 percent of the outages in an IT environment.

SQL Server 2012 helps reduce planned downtime significantly by reducing patching requirements and enabling more online maintenance operations:

•        Windows Server Core. SQL Server 2012 supports deployments on Windows Server Core, a minimal, streamlined deployment option for Windows Server 2008 and Windows Server 2008 R2. This operating system configuration can reduce planned downtime by minimizing operating system patching requirements by as much as 60 percent.

•        Online Operations. Enhanced support for online operations like LOB re-indexing and adding columns with default values helps to reduce downtime during database maintenance operations.

•        Rolling Upgrade and Patching. AlwaysOn features facilitate rolling upgrades and patching of instances, which helps significantly to reduce application downtime.

•        SQL Server on Hyper-V. SQL Server instances hosted in the Hyper-V environment receive the additional benefit of Live Migration, which enables you to migrate virtual machines between hosts with zero downtime. Administrators can perform maintenance operations on the host without impacting applications.

Few more significant merits not found in previous versions:

•        Using the WSFC APIs to perform failovers. Shared storage is not required

•        Utilizing database mirroring for the data transfer over TCP/IP

•        providing a combination of Synchronous and Asynchronous mirroring

•        providing a logical grouping of similar databases via Availability Groups

•        Creating up to four readable secondary replicas (upto 2 Sync)

•        Allowing backups to be undertaken on a secondary replica

•        Performing DBCC statements against a secondary replica

•        Employing Built-in Compression & Encryption

•        Automatic Page Repair

Eliminate Idle Hardware and Improve Cost Efficiency and Performance

Typical high availability solutions involve deployment of costly, redundant, passive servers. AlwaysOn Availability Groups enable you to utilize secondary database replicas on otherwise passive or idle servers for read-only workloads such as SQL Server Reporting Services report queries or backup operations. The ability to simultaneously utilize both the primary and secondary database replicas helps improve performance of all workloads due to better resource balancing across your server hardware investments.

Easy Deployment and Management

Features such as the Configuration Wizard, support for the Windows PowerShell command-line interface, dashboards, dynamic management views (DMVs), policy-based management, and System Center integration help simplify deployment and management of availability groups.

Contrasting RPO and RTO Capabilities

The business goals for Recovery Point Objective (RPO) and Recovery Time Objective (RTO) should be key drivers in selecting a SQL Server technology for your high availability and disaster recovery solution.

This table offers a rough comparison of the type of results that those different solutions may achieve:

High Availability and Disaster Recovery SQL Server Solution	Potential Data Loss (RPO)	Potential Recovery Time (RTO)	Automatic Failover	Readable Secondaries(1)
AlwaysOn Availability Group - synchronous-commit	Zero	Seconds	Yes	0 - 2
AlwaysOn Availability Group - asynchronous-commit	Seconds	Minutes	No	0 - 4
AlwaysOn Failover Cluster Instance	NA	Seconds -to-minutes	Yes	NA
Database Mirroring(2) - High-safety (sync + witness)	Zero	Seconds	Yes	NA
Database Mirroring(2) - High-performance (async)	Seconds	Minutes	No	NA
Log Shipping	Minutes	Minutes -to-hours	No	Not during a restore
Backup, Copy, Restore(3)	Hours	Hours -to-days	No	Not during a restore
Sybase WarmStandBy	Seconds	Minutes	No	1
Sybase MSA	Seconds	Minutes	No	Multiple