Snapshots are frozen versions of your shared folders at a specific point in time. Synology supports them on Btrfs volumes — and if your NAS with us runs Btrfs (that’s the default we set up), you can enable snapshots without further ado. They are the fastest, cheapest and in some situations only help against ransomware or accidental mass deletions.
Important: snapshots are not a backup. They live on the same hardware as the original data. If the drive dies, both are gone. Snapshots complement a backup, they don’t replace one.
What snapshots are
At the Btrfs level, the filesystem records the block references of a shared folder at a specific moment. At first, the snapshot eats no storage — it’s a pointer to the blocks. Only when you change data are the old blocks kept (copy-on-write), and the snapshot slowly starts taking up space.
The consequence: snapshots on Btrfs are cheap. You can keep dozens of them without your storage exploding.
Enabling Snapshot Replication
- Package Center → “Snapshot Replication” → Install, if it isn’t there yet.
- Open Snapshot Replication → Snapshots → set up a snapshot schedule for a shared folder.
In the schedule:
- Frequency: hourly, daily, weekly.
- Retention: how long snapshots are kept, or by which criteria.
Our recommendation for most private customers:
| Schedule | Frequency | Retention |
|---|---|---|
| Hourly | 1× per hour | last 24 |
| Daily | 1× per day at 02:00 | last 30 |
| Weekly | 1× per week, Sun 02:00 | last 8 |
| Monthly | 1× per month | last 6 |
That lets you go back to any hour of the last 24 hours, any day of the last month, any week of the last 2 months, any month of the last half year.
On Btrfs, all of that together typically takes 5–15% on top of your data volume. On 1 TB of data, that’s 50–150 GB of snapshot usage.
Which shared folders you should protect
In practice, Snapshot Replication pays off for:
- Drive folders (documents, files): definitely yes.
- Photos folders: yes, but careful — photo libraries grow, and the more snapshots you keep, the more storage.
- Backup target folders for PC/Mac: yes, because this is where most accidental deletions happen.
- System folders: no, DSM handles that internally.
- Surveillance Station folders: probably not — videos rotate anyway, and snapshots would balloon your storage fast.
You can set separate schedules per shared folder. Photo folder e.g. weekly plus monthly, Drive folder hourly plus daily.
Restoring from a snapshot
Option 1: full restore of the folder
In Snapshot Replication → Snapshots → select a snapshot → Restore.
DSM replaces the current state of the shared folder with the snapshot. Careful: everything added after the snapshot is discarded. Before you do this, save anything you want to keep.
Option 2: pulling a single file or folder out of a snapshot
More elegant, because it’s non-destructive:
- On Windows, mount the shared folder via SMB.
- Right-click a folder → Properties → Previous Versions.
- You’ll see all snapshots that contain this folder — you can browse each snapshot and copy individual files out of it.
On Mac, this works via File Station → Tools → View previous versions.
On Linux, via cd /volume1/<share>/.snapshots/<snapshot-id>/ — snapshots mount like completely normal read-only directories.
Snapshots against ransomware
Classic scenario: ransomware encrypts your Drive data. If you have snapshots active, the old versions are untouched — the ransomware writes new files, the snapshot points to the old blocks.
But: if the ransomware gets into your admin account, it can delete snapshots. Hence two additional measures:
- Enable immutable snapshots (DSM 7.2 and up): in the snapshot schedule, set a retention period for immutable snapshots, e.g. 14 days. During that period, nobody can delete the snapshot — not even an admin account, and therefore no ransomware that has hijacked one. The older “Protect snapshots” checkbox isn’t enough for this: it only prevents automatic rotation deletion, an admin can still delete protected snapshots.
- Hyper Backup to an external target: a backup with its own credentials outside your Synology. Typical ransomware that encrypts your NAS can’t reach this copy. But plain talk: an attacker with admin access will also find the stored backup task including its credentials — which is why the admin account and 2FA need securing first. Exactly for this second copy, there’s our Hyper Backup Storage — setup in the KB article.
Keeping an eye on storage usage
Snapshots grow slowly but steadily. In Snapshot Replication under Snapshots → storage analysis you can see how much each snapshot occupies.
If one snapshot is particularly large, you’ve changed a lot of data since then. For monthly snapshots, that’s normal; daily ones should stay small.
If storage gets tight: delete old snapshots or dial the schedule down to fewer snapshots.
Frequently asked questions
What if I don’t have a Btrfs volume (but ext4)? Then you can’t use Snapshot Replication. ext4 volumes have no snapshot feature. We set up Btrfs for you at ordering time — if you have an older Synology with ext4, talk to us about migration.
Where are snapshots stored?
On the same volume as the original data, in the hidden folder .snapshots. You can’t put them on a different pool — snapshots are a filesystem feature, not a separate storage structure.
Can snapshots be encrypted? Snapshots inherit the encryption of the volume or shared folder. If your shared folder is encrypted, its snapshots are encrypted too.
Do snapshots make sense on a 100% full NAS? No. When the volume is full, Btrfs can’t perform copy-on-write operations anymore — new writes fail. Keep at least 10–15% of the volume free for snapshots.
How many snapshots can a Synology handle? Technically a lot, but beyond ~1000 per volume the snapshot list in the GUI gets sluggish. Standard schedules produce 50–100 snapshots — comfortable.
Can I replicate snapshots to a second Synology? Yes, that’s the “Replication” part of the package name. Snapshot Replication can send snapshots to a second Synology — say home NAS → xaweho NAS, or between two xaweho NAS units. Setup is similar to Hyper Backup, but specific to snapshots. For most private customers, Hyper Backup is the simpler solution.
What if I restored a snapshot but still need the previous state too? DSM automatically takes a new snapshot of the pre-restore state when restoring. So you can go back.
What’s next
First login to DSM after provisioning
What to do first after ordering your Synology from us — login, language, initial security, and getting a few important defaults right from the start.
Securing the admin account on your Synology — 2FA, password, login protection
A Synology exposed to the internet is a brute-force magnet. Here's how to harden the admin account, protect against login floods and sleep better at night.
Setting up Synology Drive for file sharing and sync
Synology Drive is the Dropbox replacement on your Synology — sync client, sharing links, version history. Here's how to get it running.
Setting up Synology Photos — photo auto-upload and album management
An iCloud Photos replacement on your own hardware. How to set up Synology Photos, enable auto-upload, and use face and object recognition.