How do you use the Synology Drive sync disk? Accidental deletion can spread; I only learned the difference between syncing and backup after falling into a pitfall

last year, while organizing my computer desktop, I dragged a folder called "2024 Quotes" into the recycle bin and clicked it to clear it off on the spot. Ten minutes later, Synology Drive popped up a "Sync Complete" prompt in the corner. My heart skipped a beat. I opened the drive on my phone and checked—the one in the NAS was gone too.

that folder contained scanned copies of the quotation and contracts accumulated over two years. Fortunately, I managed to find it in the end. How I got it will be explained later. This incident made me fully understand a truth: Drive is a sync drive, not a backup drive. If you mix these two things, sooner or later you'll have to pay the tuition fee.

to clarify: synchronization and backup are two different things

many people install the Drive with the same original intention as I do: worried about losing files if the hard drive breaks, so they want a NAS as insurance. This starting point planted a landmine.

sync means "mirroring"—the computer looks exactly like the NAS side as it looks. You create a new file, and it uploads it; If you edit a file, it will follow along; you delete files, it will delete them without . Drive's loyalty is beyond imagination—even the act of emptying the recycle bin is almost as if it can execute it for you in sync.

backup is different. Backups are 'archived' to keep historical versions, and if you delete a mistake, you can revert it. What really manages backups on a NAS is something else: Hyper Backup, snapshots, or the most basic scheduled copy. Later, I wrote a dedicated article NAS How to Safely Back Up Your Data, the 3-2-1 Principle is broken down and calculated, so I won't repeat it here.

one thing to remember: sync prevents "device failure," backup prevents "slip of the hand." Drive only needs to be on the front half; the second half relies on its built-in version control and recycle bin as backup. How to turn these two switches on will be explained below.

three sync modes, I used each for a while

when creating a sync task, Drive lets you choose a mode—three in total. Don't be fooled by the similarity in name; their behavior is far from good. I've been running the DS220+ for over two years and have used all three modes long-term, so I'll share my thoughts.

two-way sync is my main mode; it's the one running between my desktop and the NAS. You can edit both sides of the file, and after editing, it syncs within seconds, making the experience smoother.

here's a common misunderstanding for beginners: many people think 'upload only' prevents accidental deletion—if you only push up operations on your computer, then you can't delete files on your NAS. At first, I thought the same way. I set my dad's computer to upload only, thinking that his files only go in and not out. Later, I tested it and found that in upload mode, when the computer deletes files, the NAS still goes to the recycle bin . Its 'only' refers to direction (changes on the server side won't be pulled down), not 'only add, no deletion.' If you want a mode where 'no matter how much you try locally, the NAS won't work,' only download it.

only downloaded I used it on the laptop at work. Since the company doesn't allow messy stuff, I set up a download-only task and pulled the database to view locally. Deleting it locally doesn't help; next time you sync it, it will come back on its own. NAS is the only one who has the final say. The trade-off is that newly created local files won't be uploaded; to submit files, you have to manually upload them via the web interface.

there's another pitfall unique to the two-way mode, called the Conflict Dungeon . Two computers have bidirectional sync enabled simultaneously and the same Excel file is changed. The drive doesn't know whose to listen to, so it simply doesn't overwrite either and generates a new file with the name "####冲突副本" in the name. The first time I saw a screen full of hashtags, I thought I was poisoned. The solution is simple: keep the correct copy and delete the other. But you have to know this happens, or your job directory will quietly accumulate a bunch of conflicting dungeons.

synchronize the directory and select the entire user drive—this is the second tuition fee I paid

my first time creating a task, I wanted to save trouble and directly checked the entire user folder—desktop, documents, downloads, and images all synchronized at once. On the first night, I synced over 180GB. The next day, when I opened the NAS, it was full of AppData, caches for various apps, and directories redirected from OneDrive with another layer of OneDrive, like a Russian nesting doll.

Later, I deleted and rebuilt the task, only checking three boxes: desktop, documents, and a dedicated work directory. The sync size dropped from 180GB to 60GB, and the sync database became lighter. After booting, the drive ran twice and then quieted, unlike before when it was chewing on cache files for half an hour of booting.

Additionally, I strongly recommend trial run the new task with a small catalog for a week . Find a few dozen MB of directories to sync for a few days, observe how they handle deletion, rename, conflicts, and other actions. Once you have a clear idea, zoom in on the directory. Don't be like me—go all-in on the first try.

if it's a small hard drive laptop (my old 128GB ThinkPad), there's a lifesaver option for two-way sync called On-Demand Sync. After opening it, the NAS files only display a placeholder locally, not on the hard drive. Double-click to open it and then pull it down on site. The 128GB C drive instantly became a relief. But on-demand sync has its own pitfalls: files that haven't been downloaded won't open when offline. Once, while on a business trip on the high-speed train, I wanted to change the plan, but double-clicking it turned out to be a placeholder, so I just stared blankly. Later, I learned my lesson. Before a business trip, I right-clicked on my frequently used folder and selected 'Always keep on this device,' and pre-nailed it to my local location.

How to fix accidental deletion: Recycle Bin and version control must be turned on first

return to the quotation folder at the beginning. It can be recovered thanks to two things, and neither is pre-installed for you—you have to drive it yourself first.

first is the Recycle Bin shared folders. In the DSM Control Panel, open the Recycle Bin for the shared folder you want to sync, then set the retention period—I set it to 90 days. Once enabled, files deleted in sync will go to the Recycle Bin and lie down, rather than evaporating immediately. My quotation sheet folder was dragged back from the recycle bin, taking less than five minutes. Note that the retention period will be automatically cleared when the retention period expires; do not treat the Recycle Bin as a cold backup.