Sync app on QNAP NAS makes NAS hang permanently every antivirus scan

[bmattis]

Since some months back I've encountered my QNAP NAS totally unresponsive once a week, needing a reboot to be usable again. With help from QNAP's support, I've narrowed the problem down to the Sync app in combination with the antivirus scan provided by QNAP:

 

- I have the antivirus scan scheduled to run once every week. One of the folders in the scan job is synced by the Bittorrent Sync app on the NAS.

- After some hour of antivirus scanning, before the antivirus reports a finished scanning, the NAS becomes impossible to reach on the network. It happens every time, and the NAS has to be rebooted. No logs show any direct clues to what happened.

- If I disable the Sync app, though, the antivirus scanning jobs always finish without a fault!

- If I re-enable the Sync app, the NAS hangs again at every scan job.

 

I don't know if QNAP or Sync (or both) is to blame for this error, but it makes Sync much less useful and reliable. Worth noting is that this error started appearing some 6 or 12 months ago, so it was introduced in some software update from Sync or QNAP, probably during early 2016 or so. I have regularly updated the NAS and Sync several times the last year. It should be mentioned though that I still run one of the last versions of Bittorrent Sync before the rebranding to Resilio, so I haven't tried out the last version and due to various bad experiences I am not currently planning on installing it. This is more of a bug report than a cry for help.

[Helen]

hm, our antivirus is ON all the time, but we never had this problem and never got any reports from other QNAP users. 

is this the built-in antivirus that you use? Can you provide any debug info, like that antivirus report, log or anything? What is exactly your scan job - how deep it's set, what folders it scan,. Are the virus definitions up to date? what is your QNAP, any details....? 

[jmpr]

I have a similar problem, but I do not have antivirus enabled. My QNAP Sync 2.38 stops responding after some hours. I have to restart the NAS to keep it running again. It happens with last versions.

[bmattis]

On 9/30/2016 at 4:23 PM, Helen said:

hm, our antivirus is ON all the time, but we never had this problem and never got any reports from other QNAP users. 

is this the built-in antivirus that you use? Can you provide any debug info, like that antivirus report, log or anything? What is exactly your scan job - how deep it's set, what folders it scan,. Are the virus definitions up to date? what is your QNAP, any details....? 

Yes, the built-in antivirus in the QNAP NAS UI.

If the Sync app is activated, the antivirus doesn't have a chance to finish and give any report. If Sync is deactivated, the antivirus doesn't find any problems, so no interesting logs or reports.

The scan job has the following settings: Scan 2 specific folders (one of which is Sync'ed), weekly, quick scan, scan compressed file content, deep scan for document files, only report the virus.

The virus definitions update daily.

My QNAP NAS is a TS-131.

[bmattis]

7 hours ago, jmpr said:

I have a similar problem, but I do not have antivirus enabled. My QNAP Sync 2.38 stops responding after some hours. I have to restart the NAS to keep it running again. It happens with last versions.

Doesn't seem very similar. My *NAS* stops responding, not my Sync app. And I *have* antivirus enabled. :-)

[Helen]

@jmpr,

you case is a different one. Perhaps RAM related. Please contact support. And before that I'd suggest updating Sync sync2.4, please see here. 

@bmattis,

Sync is a user's app, i mean runs solely in userspace, and has no access to kernel modules or system processes. Do you have any logs or dumps recorded by that antivirus? Did  the QNAP team saw them? what exactly obstacle Sync is creating for the antivirus? If the antivirus got an even it cannot handle, I'm not sure that we can debug that. 

[bmattis]

On 2016-10-04 at 0:50 PM, Helen said:

 

@bmattis,

Sync is a user's app, i mean runs solely in userspace, and has no access to kernel modules or system processes. Do you have any logs or dumps recorded by that antivirus? Did  the QNAP team saw them? what exactly obstacle Sync is creating for the antivirus? If the antivirus got an even it cannot handle, I'm not sure that we can debug that. 

No logs or dumps, since it doesn't complete the scan. No interesting dumps when Sync is disabled and the scan completes.

I have filed a ticket at QNAP a week ago, and they are remotely checking my NAS at the moment. We'll see what they say. Anyway I wanted to inform all parties that are somehow related to the problem.

[bmattis]

Now the QNAP support has done some analysis and it seems like it's a memory thing making the unit unresponsively super-slow. They say that:

 

Quote

The NAS will respond very very slow but is still alive, ssh command still works but also with very very slow response.
This model only has 512 MB memory and antivirus scan need more than 200 MB memory.

From my point of view, it could be not enough memory during antivirus scan and BitTorrent Sync running in the same time.

So please separate this kind of heavy loading services.

 

So, the NAS can simply not behave robustly when it runs out of memory -- which the user will probably not be able to know beforehand that it does.

One way I found to minimize the problem is to disable the zip file scanning in the antivirus settings, or at least to greatly reduce the size of zip files allowed for scanning. When changing that setting from 200 MB to 10 MB, the antivirus scan actually finished in a couple of hours, and the NAS was responsive (albeit not fully stable) meanwhile.

But all in all, it's about bad out-of-memory handling, so I urge all developers of Sync apps and other apps to keep their memory at the minimum instead of lazily relying on the users getting bigger and bigger systems all the time!