Replicas are not Backups!
The common pitfall
A few weeks ago I spent a few days on-site at a customer running a pretty serious infrastructure: lots of vSphere hosts with tons of VMs, external customers, OpenShift, block storage backing the VMs, and NAS storage holding and serving some very critical production data.
The infrastructure is split across two active-active sites. I want to focus on the NAS boxes, or filers, as we used to call them a long time ago. The vendor provides clustering and mirroring features. The architecture, quite rightly, is built around an active-active cluster that’s always in sync, with one node at each active site. For an extra layer of data protection, there’s also a mirror to a third box sitting in a different location from the first two.
Get ITinto Blog | Alessandro Tinivelli’s stories in your inbox
Join Medium for free to get updates from this writer.
At first glance, this seems to follow the golden 3–2–1 rule: 3 copies, 2 different sites, 1 offline. At a quick glance, sure, but the difference looks small without actually being so. What we really have here are REPLICAS, not COPIES. What’s the difference? If someone deletes the data, it’s instantly deleted on the other cluster node too and, shortly after, on the mirror copy as well.
The best practice
Since we’re talking about critical data, both common sense and regulatory requirements would demand long retention and at least 3 copies on 2 different media (boxes running the same technology and the same OS don’t count as different media), 1 of which is OFFLINE, for example on good old tape.
So in a situation like this, you need to start backing up the filer ASAP, ideally with an enterprise backup product from your vendor of choice. That gets you three things: the data lives on a different technology; just as important, you get retention that meets both regulatory and business requirements; and finally, and by now essential, you get a copy that’s offline, and even better offsite too, so that neither a fire nor a cyberattack can touch it.
The rules
BACKUP is always a must
REPLICATION is not BACKUP
OFFLINE copy is mandatory
