Software-Only HA and DR for Linux – LINBIT Briefing Note

Linux is the dominant operating system of most cloud providers, and many enterprises have mission-critical applications that run on Linux. The applications running in these environments can be on bare metal systems, or virtual machines as well as containers.

All of these use cases have Linux-based applications that need to be highly available and protected from disaster. The problem is that providing these solutions requires a proprietary storage system with built-in HA and replication. Linux administrators need a software-only solution that is simple to set up and works with a variety of software and architecture designs. While newer solutions like CEPH can work, a full-scale CEPH installation is complex and beyond requirements of most organizations..

The Value of Software Only HA and DR

The primary value of a software-only HA and DR solution is the flexibility that it provides. Data can be mirrored or replicated from any volume to any volume from any vendor to any location, including the cloud. This flexibility is especially important for Linux administrators since being flexible is a core tenet of their architectures.

Without the flexibility of software-only HA and DR, administrators are forced to use proprietary storage hardware solutions that, while they have HA and DR built-in, must perform these functions to a similar system from the same manufacturer. The new emerging alternative is to use Software Defined Storage solutions made for Linux to address HA and DR. CEPH is an example. The packages provide the HA and DR functionality but are relatively complex to set up, and useful only for relatively large installations.

Beyond flexibility, software only HA and DR solutions provide greater resilience. Replication can occur from one Linux server, virtual machine or container to another; shared storage is not required. Hardware only HA and DR solutions can typically only replicate between storage systems. The hardware and the customer’s budget is limited in the number of replicas is can create.

The LINBIT Alternative

LINBIT provides a software solution called DRBD. It is a software-only HA and DR solution designed specifically for Linux. It has been available for more than a decade, it has been in the Linux kernel for many years, and has been downloaded over 1.7 million times. DRBD can seamlessly copy data as it changes from one Linux volume to up to 31 other volumes. Since the DRBD target can be any other Linux block device, the cost to set up a simple replication strategy to achieve basic HA is very cost-effective making DRBD attractive to medium-sized data centers or enterprises that may only have a limited deployment of Linux.

LINBIT solutions build on their core open-source DRBD solution which provides a synchronous mirror between two storage volumes, on different servers.

LINBIT DRBD proxy adds asynchronous replication capabilities to DRBD, enabling true disaster recovery. The copies can be replicated asynchronously. The software also supports one-to-many replication, with as many as 31 targets. Armed with DRBD and DRBD proxy an organization could synchronously mirror a copy of data to another on-premises server. It could then asynchronously replicate data to a remote site within the region and then again to another site on the other side of the country. Ordinarily, the cost of this type of protection, with turnkey hardware solutions, would make it impractical for most organizations to provide, but DRBD makes it possible.

DRBD capabilities, like creating or removing volumes and taking snapshots of that volume. It also supports consistency groups, so an application spread across multiple volumes will have its data captured consistently. LINBIT’s SDS solution adds the ability to create storage pools and the ability to locate the best place to provision storage. It also provides the ability to select “fast” or “slow” storage.

StorageSwiss Take

The first requirement of most Linux environments as they scale is for IT to provide high availability and disaster recovery for applications as they come on-board. For many IT planners, moving to Linux or a Linux VM/Container environment is the first step to IT modernization. Consequently, IT planners need to consider carefully, how they will provide HA and DR. Instead of being locked into the methods of the past, they should consider a more open, storage neutral solution that will increase flexibility while driving down costs.

Twelve years ago George Crump founded Storage Switzerland with one simple goal; to educate IT professionals about all aspects of data center storage. He is the primary contributor to Storage Switzerland and is a heavily sought after public speaker. With over 25 years of experience designing storage solutions for data centers across the US, he has seen the birth of such technologies as RAID, NAS and SAN, Virtualization, Cloud and Enterprise Flash. Prior to founding Storage Switzerland he was CTO at one of the nation's largest storage integrators where he was in charge of technology testing, integration and product selection.

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