QNAP NAS- How to Fix Snapshot Problem

qnap nas snapshot

 

Introduction

 

I recently had a problem with my QNAP TS-651 NAS where there seemed to be a “ghost” snapshot. The system alarmed at the NAS , so I went to the web interface to find out I was getting a threshold reached warning on my data volume. After sifting through Storage Manager, it became obvious that it was being caused by snapshots. The only problem was, Snapshot Manager wasn’t showing any snapshots at all!

My first attempt to clear up space on the volume was deleting some old security camera recordings, but then the rogue snapshot grew to take up that space too. I have my snapshots set to 10% reserved space. When that fills up, it should delete the old one. I think the problem with my set up is that it will never reach the 10% allocation without alarming, because my data volume is thin-provisioned and takes up 90% space. The was poor planning on my part, but it has nothing to do with the actual problem of a snapshot not showing up in Snapshot Manager.

The biggest drawback in this situation is that even though my data volume is only half full (around 6 TB out of 12 TB used), the system is basically seeing the storage pool as full. Services such as Qsync started shutting down, and I couldn’t delete files in File Station. I think this is a ridiculous way to do things, especially for those of us who are used to the way Windows works, but apparently that’s the way things are in QTS.




Here’s a few other screenshots detailing my situation:


Slideshow- Tap or click to view
qnap nas snapshot

But when you investigate the snapshots, you see there aren’t any there.

qnap nas snapshot

The system thinks there’s a snapshot taking up space (and there probably is), but it doesn’t show it in Snapshot Manager either.



This information was pulled from this post at QNAP NAS Community Forum .

The Solution

 

To fix the problem, download PuTTY if you don’t already have it installed. Then follow the steps outlined in the slideshow below. Be warned- deleting the ghost snapshot caused the NAS to flag my data volume for a file system check, which took a while to complete (about an hour for a 13TB volume). During this time the NAS will shut down most services and it won’t be usable for file operations until it’s done. Also, I highly recommend that you manually stop all apps from the App Center before starting the scan.


Slideshow- Tap or click to view
qnap nas snapshot

Type in the command lvs  to locate the problem snapshot.

qnap nas snapshot

The first two columns contain the info we need: snap20002  and vg1.

qnap nas snapshot

We’ll use that info for the next command: lvdatac vg1/snap20002 ––discard. Notice the space before the dashes and there are two dashes on discard.

qnap nas snapshot

The system will start working, but won’t tell you what it’s doing. Type in: dmsetup status vg1-snap20002. You’ll see a row of columns. Column 4 is the one we’re concerned with. There are no spaces between the dash.

qnap nas snapshot

You can type that command in periodically (it might take a while for the system to finish what it’s doing). Notice column 4 is counting down.

qnap nas snapshot

When column 4 reaches 0, you’ll see Ready Success. Now you’re ready to continue.

qnap nas snapshot

The next command is lvremove vg1/snap20002.

qnap nas snapshot

Confirm that you want to delete the snapshot by typing Y.

qnap nas snapshot

Go back to the web UI. Notice the dashboard icon isn’t orange anymore.

qnap nas snapshot

You can open it up and see System Health doesn’t have a warning attached anymore.

qnap nas snapshot

Click on the menu in the upper left.

qnap nas snapshot

Click Storage Manager to open it up.

qnap nas snapshot

Click Storage Space, then Manage.

qnap nas snapshot

You can confirm the problem snapshot is gone (0 MB). Click Close.

qnap nas snapshot

An unfortunate side effect is that you might need to repair your file system. Click the link to start the process.

qnap nas snapshot

You’ll need to confirm that you want to check the file system. This will stop all services so the volume can be unmounted and scanned. This will take a long time and you won’t have access your files while the operation is in progress.

qnap nas snapshot

Again, you’ll be warned that you won’t be able to use the NAS until the scan and repair operation is completed. Click OK if you want to start it.

qnap nas snapshot

You’ll see the scan begin. For a TS-651 with 13 TB of space, this took about an hour to complete.



Conclusion

 

Although the QNAP TS-651 is generally a reliable server, occasionally it does hit small, annoying speed bumps. I haven’t had to use the snapshot feature to perform a recovery, but it would be nice to have if that ever happens. Aside from that, it’s also good knowing that I have the primary NAS functionality back- everyday file operations as the backup server for my WHS 2011 box, and Qsync, which I’ve become more and more reliant on to backup photos from my phone.

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About Adam Bollmeyer

I'm a home technology enthusiast with a penchant for home automation, networking, and computers. My goal is to help others improve their knowledge of how available technology can be used at home.