The first time I really understood why snapshots matter, a friend called me in a panic because a synced folder on her DS920+ had propagated a corrupted spreadsheet across every device she owned. The good file was gone from the cloud, gone from her laptop, gone from her phone.
Except it wasn't gone from the NAS. A snapshot from three hours earlier still had the clean copy, and we had her working again in under two minutes.
That is the whole pitch. Btrfs snapshots on a Synology are a local time machine for a shared folder, and setting them up properly takes about ten minutes.
What a Btrfs snapshot actually is
A snapshot is a frozen, read-only picture of a shared folder at a single moment in time. It is not a copy in the way you might think, so it does not duplicate all your data.
Because Btrfs uses copy-on-write, a fresh snapshot takes almost no space at first. It only starts consuming storage as files change afterward, since the filesystem keeps the old blocks around so the snapshot still points to them.
In practice this means you can keep dozens of snapshots of a busy folder and spend only a few percent of extra capacity. If you want the underlying mechanics, the Btrfs filesystem overview explains copy-on-write in plain terms.
Here is the mental model I give people. A snapshot does not save your files, it saves a bookmark to exactly how the folder looked at 2:00pm on Tuesday, and Btrfs promises to never throw away the blocks that bookmark points at until the snapshot is deleted.
That is why deleting a snapshot is instant and why creating one is too. Nothing is being copied in either direction.
Install Snapshot Replication
DSM handles snapshots through a package called Snapshot Replication, and it is free.
Open Package Center, search for Snapshot Replication, and click Install. It pulls in a small dependency or two automatically and takes maybe thirty seconds on most models.
Once it is installed you will find it in the main menu as its own app. That is where every setting for scheduling, retention, and recovery lives.
A note on models and DSM versions
Everything here assumes DSM 7.x, which is what most people are running in 2026. The steps are nearly identical on DSM 6.2, though a couple of menus sit in slightly different places.
Plus-series units like the DS220+, DS920+, and DS1522+ all support Btrfs. Some entry J-series and Value-series boxes do not, so confirm on the Synology product pages if you are unsure about your exact model.
Create your first snapshot schedule
Open Snapshot Replication and go to the Snapshots tab on the left. Pick the shared folder you care about most, something like home, photo, or a documents share, and select it.
Click Settings, then the Schedule tab, and tick Enable snapshot schedule. Now decide how often DSM should take a picture.
- Choose a frequency. For a documents or working folder, every hour during the day is a sweet spot. For a media library that barely changes, once a day is plenty.
- Set the active window. You can limit snapshots to, say, 8am through 8pm on weekdays so you are not capturing an idle folder at 3am.
- Enable advanced retention. This is the setting that keeps you from drowning in snapshots, and I cover it next.
While you are in the Advanced tab, look for the lock option. Locking a snapshot marks it immutable, which means retention will never auto-delete it and, just as importantly, an attacker who compromises an admin account cannot wipe it either.
I lock one snapshot per month on my most important share. It costs almost nothing and gives me a guaranteed clean restore point even in a worst-case ransomware scenario.
Set retention so you keep the right history
Retention is where snapshots go from a neat trick to an actual safety net. Without it, you either keep too few and lose the version you need, or keep thousands and confuse yourself.
DSM offers two modes. The simple one just keeps the latest N snapshots. The advanced one, which I use on every system I touch, keeps a smart pyramid.
| Retention rule | Example setting | What you get |
|---|---|---|
| Hourly | Keep 24 | Roll back any hour of the last day |
| Daily | Keep 7 | Any day of the past week |
| Weekly | Keep 4 | Any week of the past month |
| Monthly | Keep 6 | Half a year of monthly checkpoints |
That whole set is roughly 41 snapshots, and on a normal home folder it costs only a small slice of capacity. You get fine-grained recent history and a long tail of older checkpoints without keeping every single one.
Synology caps snapshots at 1,024 per shared folder, so retention also stops you from ever hitting that wall.
Recover a file from a snapshot
This is the part that pays off. Say someone overwrites a budget file at 2pm and notices at 4pm.
In Snapshot Replication, go to Recovery, pick the shared folder, and you will see a list of snapshots with timestamps. Select the 1pm one, click Browse, and DSM mounts that read-only version.
If you enabled the visible snapshot trick earlier, there is an even faster path. Open the share in File Explorer, go into the #snapshot folder, and each subfolder is a full timestamped copy you can drag files out of like any normal directory.
That second method is the one I hand to non-technical family members, because it needs zero DSM knowledge. They just open a folder, find yesterday's version, and copy it back.
- Find the file you need inside the browsed snapshot.
- Copy it out to a safe spot, or restore the whole folder if the damage is widespread.
- For a full rollback, use Restore, but read the warning first because it reverts the entire share to that point.
Snapshots are not a backup
A mistake I see constantly is people treating snapshots as their backup and stopping there. Snapshots live on the same drives as your data, so a dead volume or a stolen NAS takes the snapshots with it.
Use snapshots for fast recovery from human error and ransomware, then pair them with a real off-box copy. Hyper Backup to an external USB drive or a cloud target covers the disaster case, and the classic 3-2-1 backup strategy explains why you want both.
Think of it as layers. Snapshots handle the oops moments, backups handle the house-fire moments.
Where I would start today
If you do nothing else, enable hourly snapshots with advanced retention on the one folder that would ruin your week if it vanished. That single change has saved more of my clients' weekends than any other setting in DSM.
Then, once you trust it, add your photo and document shares and let the retention pyramid do the rest quietly in the background.
Frequently asked questions
Do Btrfs snapshots slow down my Synology?
In normal home use the impact is negligible. Taking a snapshot is nearly instant because it just records the current state, and copy-on-write adds a tiny overhead on writes that you will not notice on typical file activity. Very heavy, constant write workloads can feel a slight difference, but browsing photos and saving documents will not.
How much disk space will snapshots use?
A brand new snapshot uses almost nothing. Space is only consumed as files change after the snapshot is taken, since the old blocks have to be kept. On a typical documents folder, a full retention set of 40 or so snapshots often costs only a few percent of the folder size.
Can I snapshot a folder if my volume is formatted as ext4?
No. Snapshots are a Btrfs feature, so the volume holding the shared folder must be Btrfs. There is no in-place conversion, so you would need to back up your data, delete and recreate the volume as Btrfs, then restore. Check the volume format in Storage Manager first.
What is the difference between a snapshot and Recycle Bin?
Recycle Bin only catches files you delete, and only if it is enabled. Snapshots capture the entire state of the folder, including overwritten and modified files, at scheduled points in time. Snapshots also protect against ransomware that Recycle Bin cannot, since they are read-only.
How many snapshots can I keep per shared folder?
Synology DSM allows up to 1,024 snapshots per shared folder. That sounds like a lot, but a busy hourly schedule can approach it, which is exactly why advanced retention exists. Retention automatically prunes older snapshots so you never hit the limit.
Will a snapshot protect me from ransomware?
Largely yes, because snapshots are read-only and ransomware running on a client PC cannot alter or delete them the way it encrypts live files. If your files get encrypted, you can roll back to a clean snapshot from before the attack. Just make sure snapshot admin access is well protected so an attacker cannot delete them from DSM itself.
