Author Topic: Very slow Full System Scan  (Read 42635 times)

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Offline BTIsaac

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Very slow Full System Scan
« on: February 01, 2012, 03:40:42 PM »
I tried to look this up but apparently nobody else encountered this problem.

I usually run a full system scan at least once a day, the duration of which is between 18 and 23 minutes. Heuristics sensitivity is set to High, Scan for PUP's is enabled, Scan Whole Files is disabled - these are the settings I always scan with, unless I enable Scan Whole Files.

When I ran a scan today, I noticed that it takes unusually long. It has been running for over 14 minutes, and it barely got through the My Documents folder, which usually takes 1-2 minutes to complete. This never happened before.

I stopped the scan and tried a second one. I noticed that Avast slows down while scanning the My Pictures folder, which has about 1000 picture files saved into it. It normally doens't take 12 minutes to scan it but now it does. Everything else is scanned at the usual pace. Scan Speed displays 6-10 MB per second, which is clearly false. No settings have been altered since the last scan. Enabling or disabling Scan Whole Files makes no difference. Scanning the folder manually takes 4 minutes, significantly less time, so this only applies while running a full system scan.
The only significant thing that has changed on the computer was the signature database update. about 5 hours ago. Does anyone have any idea as to what could be causing this?

Offline Ragamuffin

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Re: Very slow Full System Scan
« Reply #1 on: February 01, 2012, 03:56:22 PM »
I've noticed this too. Scanning on my main system drive (which is SSD) is quick and normal, but when it switches over to my storage drive which is full of media files, pictures, music, videos, etc, (which is a regular HDD) it slows right down. Before today's definitions update my scans were about 12mins max, now it's taking around 50mins.

Offline Pondus

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Re: Very slow Full System Scan
« Reply #2 on: February 01, 2012, 03:57:37 PM »
Quote
I usually run a full system scan at least once a day,
why?


Quote
Heuristics sensitivity is set to High, Scan for PUP's is enabled,
why?....and do you know what PUP is?





Have you tried this?......does it change anything ?
https://blog.avast.com/2010/04/25/how-to-make-the-full-system-scan-6x-faster-in-10-days/

Quote
Tip: to make the Full System Scan even faster, configure it to actually take advantage
of the persistent cache. To do this, open the Full System Scan details, click the Settings button and check the box “Speed up scanning by using the persistent cache” on the Performance page.


« Last Edit: February 01, 2012, 04:01:36 PM by Pondus »

Offline BTIsaac

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Re: Very slow Full System Scan
« Reply #3 on: February 01, 2012, 04:02:37 PM »
Quote
I usually run a full system scan at least once a day,
why?

OCD. Don't ask.

Quote
Quote
Heuristics sensitivity is set to High, Scan for PUP's is enabled,
why?....and do you know what PUP is?

A) Just to be sure and B) Yes I know, more or less - never really found any though.

How is any of this relevant?

Quote
Have you tried this?......does it change anything ?
https://blog.avast.com/2010/04/25/how-to-make-the-full-system-scan-6x-faster-in-10-days/

I specifically asked WHAT is causing this sudden change, not how I can bypass it. If how to enable persistent cache is all I wanted to know, I wouldn't have registered an account.

I've noticed this too. Scanning on my main system drive (which is SSD) is quick and normal, but when it switches over to my storage drive which is full of media files, pictures, music, videos, etc, (which is a regular HDD) it slows right down. Before today's definitions update my scans were about 12mins max, now it's taking around 50mins.

So it's not just me. I've noticed dramatic increase in scanning speed before but it involved the "Scan Whole Files" option. Regular scans were not affected.
« Last Edit: February 01, 2012, 04:08:33 PM by BTIsaac »

Offline DavidR

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Re: Very slow Full System Scan
« Reply #4 on: February 01, 2012, 04:17:14 PM »
- With a resident on-access antivirus like avast, the need for frequent on-demand scans is much depreciated. For the most part the on-demand scan is going to be scanning files that would be otherwise be dormant or inert. If they were active files then the on-access file system shield would be scanning them before being created, modified, opened or executed.

I have avast set to do a scheduled weekly Quick scan, set at a time and day that I know the computer will be on. If for some reason my system wasn't on, no big deal I will catch up on the next scheduled scan.

Another option is the screensaver scan that will run when your system is inactive and the screensaver on. This will cycle through your system and continue from where it left off (when it starts again) if the system becomes active.

####
Well the "Scan Whole Files" option, is disabled by default as it is an unnecessary overhead, so when you make changes to the default scans/settings, you are going to incur a performance hit. The whole point of the avast default settings and the Quick and Full System scans is that they provide a good palance between protection and performance.
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Offline Pondus

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Re: Very slow Full System Scan
« Reply #5 on: February 01, 2012, 04:26:03 PM »
Why? = just me curious.....and David`s answer explains what i was thinking   ;)


Quote
I specifically asked WHAT is causing this sudden change,
do not know.....but some interesting read in that article
« Last Edit: February 01, 2012, 05:23:03 PM by Pondus »

Offline CahosRahneVeloza

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Re: Very slow Full System Scan
« Reply #6 on: February 01, 2012, 04:37:01 PM »
OK, for a minute there I thought my Hard Drive's just going bye, bye because of the veeeeery slow Full system scan issue.

Yes, I too am currently experiencing this & in fact as I am typing my post Avast! is still going through my media files.

My storage drive is big... 300GB of music, videos & games & every few days or so I do a full system scan just to make sure.... more so if I tread on sites I'm not very familiar with.

My machine isn't very fast & Avast needs to scan a lot of stuff, all in all a regular full scan for me takes only 43 minutes. But currently, it is already 1 hour & 36 minutes & the scan is still going! 0_o

It seems this latest definitions & program updates has messed up Avast's ability to quickly scan mp3 files & yes I specifically mean mp3 files. The drop in scanning speed occurs only with mp3 files dropping scan speeds to somewhere between 11~10MB per second. But once the scan gets by mp3 files the speed regains its normal 20~24MB per second rate.

I really hope the folks at Avast! technical support will get word on this & have a fix out soon as this is a bothersome situation we are currently in.

Offline DavidR

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Re: Very slow Full System Scan
« Reply #7 on: February 01, 2012, 05:15:50 PM »
If you don't mention the scan settings and if you have made any changes to the defaults, etc. as previously mentioned we really can't say why.

Same pack drill though on-demand scans are much depreciated in a resident on-access antivirus.
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Offline CahosRahneVeloza

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Re: Very slow Full System Scan
« Reply #8 on: February 01, 2012, 05:29:05 PM »
@DavidR:Whoops!

I forgot that bit of information, silly me...

Anyway...

Heuristic Sensitivity - high
Use code emulation - checked
Scan for PUPs - Checked
Follow links during scan - checked
Test whole files - unchecked

Are these what you asked for?

And no, I haven't changed any of those in the past day or weeks.


Offline ady4um

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Re: Very slow Full System Scan
« Reply #9 on: February 01, 2012, 05:59:39 PM »
The engine and definitions updates can change several things, including how certain types of files can be scanned, which modifies the scanning speed too.

Unfortunately, if there is some speed change, only avast developers can change, correct, improve or answer this question. All we can do in this regard is guess.

Most of us, forum members, have no way to answer this question, unless already answered elsewhere by Avast Team.

Keep paying attention, sporadically, to the scans, and I guess it is probably going to change again (according to changes to the engine).
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Offline dagrev

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Re: Very slow Full System Scan
« Reply #10 on: February 01, 2012, 06:30:44 PM »
My full scan on a HD with about 150GB and only 50% full takes about an hour and 45 minutes.  I'm be thrilled with a 30 minute scan.  My quick scan taks almost that long. (with the prescribed settings in place.)
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Offline DavidR

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Re: Very slow Full System Scan
« Reply #11 on: February 01, 2012, 06:43:43 PM »
@ CahosRahneVeloza
Setting the Heuristics to High (not a default setting) will have an impact on system performance, especially on a system that isn't particularly fast, etc. whilst a scan is going on.

Whilst you say you have change nothing else, avast's continually updates the avast signatures (and scanning engines) to improve detections one of those recent improvements is in the area of heuristics, with new more strict checks when heuristics are set to High. So this may be what you are experiencing.

So for me, I have Heuristics on High I don't test whole files, I don't scan for pups and I don't follow links. I also don't do a Full scan but a Quick scan and for that code emulation isn't enabled either. I never scan archives a waste of time for inert files.

So my suggestion would be to either schedule your scan for a time when the system will be on and not particularly active or just use the Default Quick scan.
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Offline CahosRahneVeloza

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Re: Very slow Full System Scan
« Reply #12 on: February 01, 2012, 06:53:26 PM »
I know the High heuristics setting is not a default setting but I've had it set to high from the first time I installed Avast as a "preferred" setting & had not encountered any issues with it until today.

Offline DavidR

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Re: Very slow Full System Scan
« Reply #13 on: February 01, 2012, 07:25:37 PM »
As I said there will always be changes to the virus signatures and the scanning engines to improve detection and that can have an impact.

I however, have not seen that impact in my Quick scan with heuristics on High and the settings as mentioned. Why you find the difference only today, I don't really know as upgrades to the heuristics (when set to high) occurred a little time ago (not sure of the exact date). Unless you haven't done a scan for some time.
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Offline dagrev

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Re: Very slow Full System Scan
« Reply #14 on: February 01, 2012, 08:05:23 PM »
DavidR- Just curious, but why not scan links (which I think is default)?  Because where the path leads back to has unimportant and most likely no bad files?
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