In Part 1 of this blog series, we discussed why traditional solutions face challenges when trying to provide incremental-forever backups for large databases. We highlighted that the most efficient way to achieve this is to maintain snapshots in time, tracking the changed blocks between points in time. And we pointed out that what’s needed is a mechanism to identify changed blocks between snapshots in a way that is portable – where point-in-time copies can be moved around to wherever you need them – off site for DR, in the cloud for long term retention, in another cloud for resiliency – wherever the need is. That requires some real innovation and is exactly what Actifio’s Virtual Data PipelineTM (VDP) provides to you.
So let’s dive into the details. In order to capture incrementally-forever, you need three things:
- A way to get the database to a consistent state on disk so that a snapshot will have data integrity and consistency.
- A way to take a snapshot of volumes, to serve as a temporary, stable source from which to retrieve data – initially a full copy and then the changed blocks ever after.
- A way to track changed blocks between two points in time.
At Actifio, we always try to use whatever mechanisms already exist to do those things, but in most cases we’ve had to augment those with technology we developed on our own. Like in the three little pigs story, it takes hard work to get the results you want, but we believe it’s worth it. So let’s look at how Actifio handles three major databases: Oracle, Microsoft SQL Server, and SAP HANA.
Oracle has some great mechanisms that are built into their standard RMAN (Recovery Manager) utility. Leveraging RMAN’s ability to get a copy of the database as an image – either a full copy or just the changed blocks, means that Oracle does the heavy lifting for you. That’s why some vendors claim that they support incremental-forever Oracle backups. But mastering all the complex Oracle environments is still not that easy, so it’s worth verifying that all your needs are covered.
For example, while Oracle gives you the changed blocks, you need to also handle them in a way that will allow instant recovery. For that, Actifio initiates an Oracle incremental merge operation as part of every backup, taking the latest changed blocks and having Oracle apply them to the previous backup. Of course, we keep a snapshot of the previous backup before doing that, so that we end up with a series of point-in-time snapshots that are virtual full copies and ready for immediate access. While doing that, we also manage archive log backups to make sure you can recover to any point in time by rolling logs forward (an easy drag-and-drop operation from the UI).
Another complexity is that Oracle can run database files on a file system or using Oracle Automatic Storage Management (ASM), where Oracle manages the storage directly, without an intermediary volume manager and file system. Actifio fully supports both modes and can match your production layout, presenting to the host a target for the backup that is in your preferred format – a file system or an ASM disk group. This allows you, for example, to recover an ASM database nearly without any downtime because you can bring up a database running directly from the Actifio backup, presented as an ASM disk group, and then migrate the data into whatever storage you want to use, while the database is up and running, using ASM rebalance operations.
In Part 3 of this blog series, we’ll discuss how Actifio provides incremental-forever backups for Microsoft SQL Server and SAP HANA.