TL;DR: Immutable backups stop deleted files from ever being purged, giving you a true last line of defence against data loss.
We recently worked with a client whose entire business runs on one shared database, the kind of system where a few missing files could mean real operational damage. Their standard backup setup was solid, but it had one gap: once a file’s retention period expired, it was gone for good. That conversation led us to immutable backups, and it’s a feature more businesses should understand.
Normally, when a file is deleted from a shared drive or user account, your backup system keeps a copy for a set retention period, typically 28, 60, or 90 days, before purging it automatically. That’s fine for everyday housekeeping, but it assumes nobody will ever need that file again after the window closes.
Immutable backups remove that assumption. Once enbaled, deleted files are never automatically purged. They stay in the backup indefinitely, until someone deliberately changes the retention policy. Nothing disappears in the background.
Standard retention windows exist for a reason: most deleted files really are safe to remove after a month or two. But every business has the occasional exception, a contract, a client record, a financial document that turns out to matter long after anyone expected. Immutable backups mean that file is still there, even six months on.
This is where immutability earns its keep. If an account is compromised, or someone, deliberately or accidentally, deletes a large volume of data, a standard backup will quietly start counting down to permanent removal. An immutable backup doesn’t. Nothing gets purged from the backup even if it’s already gone from the live environment, which makes it a genuine last line of defence when the data in question is critical to how the business operates.
There’s no upfront cost to switch it on. The trade-off shows up over time: because nothing is ever purged, your backup storage keeps growing, including duplicate files and data nobody actually needs any more, sitting alongside the records that genuinely matter.
Storage is billed per GB, and pricing improves as volume increases, so the cost curve flattens out the more data you hold. It’s a manageable trade-off, but one worth planning for rather than discovering six months in.
This is the question we always come back to with clients considering immutability. Backing up an entire shared drive by default is the easy option, but it’s rarely the smart one: you end up paying to store data indefinitely that was junk to begin with. The better approach is to review what’s actually in scope first, what’s business-critical, what’s duplicated, and what can sit on a standard retention policy instead.
That review is usually quick, and it means your immutable backup protects what actually matters to the business, without ballooning storage costs on data nobody will ever ask for again.
If your business runs on a system where losing the wrong file at the wrong time would be a real problem, it’s worth having this conversation before you need it, not after. Our managed cyber security team can help you work out what’s worth making immutable, and what isn’t.
Got questions about immutable backups for your business? Click here to get in touch with Chris.
