Having recently returned from my 6th Red Hat Summit (RHS), I’m writing this blog to answer a common question: “why replicate at the block level?” Using block-level replication, we can easily add high availability or disaster recovery features to any application that doesn’t natively support them.
The most frequently asked question we heard at RHS was, “how do you compare to [insert application replication OR filesystem here?]”. In most cases, the answer was, “LINBIT’s replication software, DRBD, replicates data at the block level.” It would be an extreme task to run performance comparisons vs all of the other replication technologies on the market, so generally we provide background information, including:
- DRBD can usually replicate with 1-3 percent overhead to the cluster’s backing disks, as measured by FIO
- In dual-primary mode, overhead increases to 15-20 percent
- DRBD is compatible with any application or Linux filesystem, and is effective at replicating multiple applications simultaneously.
- DRBD has a read-balancing feature. If you are running a read intensive application, DRBD will pass through reads to secondary nodes once the primary is running at maximum capacity, enabling you to leverage all of your replicated systems. One test showed 1.7x the read performance compared to the advertised speed of the drive.
Deduplication and Compression
Generally, it comes down to efficiency. EMC, NetApp, and the other big storage players use block level replication in their appliances because this way the replication doesn’t need to go “all the way up the stack.” It enables flexibility, stability, and performance. And now, Red Hat has given us one more reason to replicate at the block level: Deduplication and Compression.
In the most recent Red Hat Enterprise Linux 7.5 release, Red Hat announced integration of Red Hat VDO, or Virtual Data Optimizer. VDO is used for deduplication and compression of Linux environments. Though it can be paired with other replication technologies, it can only be fully leveraged when the replication sits underneath the VDO device. Why? You want to deduplicate and compress your data before replicating it for efficiency gains.
Effective transfer times
According to Louis Imershein, Red Hat’s Principal Product Manager for data reduction technologies, “Solutions like LINBIT’s DRBD are able to capture data below the VDO layer. This means that datasets that benefit from deduplication and compression get replicated in their dehydrated form. With less data to move, Red Hat Enterprise Linux customers with LINBIT DRBD can benefit from faster effective transfer times and reduced bandwidth requirements.”
So, as you’re thinking about underlying storage for your applications, ensure you are using a solution which allows you to maximize the benefit of the existing Linux utilities built in, and around, your Operating System. Thanks to Red Hat, block level replication is now more important than ever.