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CEPH Storage is Ideally Suited for Disaster Recovery (DR) Infrastructure

CEPH storage from Virtunet has all the features of traditional iSCSI SAN with the exception that it is reasonably priced because it uses commodity servers with all off-the-shelf hardware. And so it is ideally suited for backup and DR storage which needs to be cheap above all else.

Why deploy DR infrastructure when you already have backups?

The main reason to deploy DR infrastructure is to protect against the rare case when you lose your entire datacenter. In case of a datacenter wide outage, you can flip over to your offsite DR datacenter. The DR datacenter is a replica of your entire production infrastructure, from applications running in VMs to servers, storage, and network configuration.

DR and backups though related are two different things involving slightly different processes and underlying technologies, resulting in different times to restore the VM state and data.

Other than the rare datacenter wide outage, there are more frequently occurring failure situations where leveraging DR infrastructure is a better choice than restoring from backups. For instance, even if one VM were to fail, you can flip over to the replica of that VM in your DR site and have end users use the replica VM as the interim production VM till you restore your primary production VM. You can restore your production VM from your replica VM while in parallel the replica VM is being is being used by end users (as the interim production VM).

With DR infrastructure, you can also search and replace corrupt or deleted files, databases, mailboxes, across all VMs without restoring the VMs.

Provided you have available rack space, and if you already have a process for doing backups in place, the incremental cost to deploy DR is not too much either. You can repurpose older servers to use as DR VMware hosts and DR SAN storage (how to repurpose older servers to build SAN storage is described in later sections), then you need VMware Essentials licenses ($600), and lastly you need a backup/DR software. A software like Veeam that you might already be using for backups, has DR functionality in its basic license, so no additional licensing cost are incurred here.

What is CEPH storage?

CEPH is open source storage software that runs on commodity servers. It clusters servers together and presents this cluster of servers as a storage appliance. Virtunet Systems has enhanced CEPH by developing an iSCSI software module, VAAI and ODX (storage offload for VMware and Hyper-V) functionality, an easy to use GUI, and improving the performance of CEPH by caching to in-host SSDs or RAM. Virtunet’s rendition of CEPH is called VirtuStor.

Servers of any make, model, size, and antiquity can be ‘hot’ added to an existing CEPH cluster to add capacity or improve performance.

Why is CEPH suitable for shared DR storage?

CEPH storage has its origins at cloud service providers (SPs). The fact that commodity servers can be used to build SAN storage was important to cloud SPs to keep their hardware costs low. Low cost storage is a key requirement for on-premises DR storage simply because it is not primary storage.

Since CEPH is used by cloud SPs, it also has features to isolate and encrypt data and storage I/O path between multiple organizations that might be using the same CEPH storage cluster, a requirement if different organizations are to share the same storage hardware.

As you scale out the storage cluster, cost per capacity reduces dramatically. Starting at $2/GB for raw 5TB storage, the cost drops to 20 cents/GB for 300TB of storage. And so it is cost effective for smaller IT departments to pool together their DR/backup budgets to get larger amounts of storage for their DR infrastructure.

Sharing compute using VMware

VMware lends itself well to a shared DR infrastructure as well. Since each VMware physical server can host a maximum of 512 VMs, large number of VMs can be deployed on only a 2-host VMware cluster.

DR Infrastructure at CiiNow

  1. 2-host compute cluster using VMware essentials license running on repurposed servers. The VMware license costs $600 for both the servers.

  2. 3-server VirtuStor CEPH cluster for iSCSI storage using repurposed servers with new storage media. It has raw capacity of 24TB and usable of 12TB. The cost for the 12TB usable is $15K.

  3. Veeam is used to replicate data from CiiNow’s production VMware cluster to this DR infrastructure. The cost of Veeam Enterprise Plus Essentials is at $7K.

  4. The total cost of the entire infrastructure, with one time services fee to put together, was $30K.

This infrastructure has the spare capacity to accommodate the DR workload for a few more SMBs the same size as CiiNow, by adding a few more hard drives and SSDs.

The incremental cost to share CiiNow’s DR infrastructure was $10K per year for replicating 30 or so VMs and 10TB of data.

Furthermore, both VMware and CEPH storage cluster can be scaled up by adding more servers to each cluster, to support hundreds of SMBs with a single clustered DR environment.