Author Topic: Avast so slow scaning  (Read 4909 times)

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Offline marc-d-l

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Avast so slow scaning
« on: April 05, 2010, 03:06:56 AM »
Why is avast taking so long to do a complete scan? 1 hour 37 minutes to do 178077 files.That's on my PC with 2 gig memory and 235 hard drive.Twice as long on my other PC's using xp.
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Offline DavidR

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Re: Avast so slow scaning
« Reply #1 on: April 05, 2010, 04:50:35 AM »
Well it is almost impossible to say as you give no information on the scan you did, Full/Custom scan, including sensitivity, archives, amount of date on the HDD and amount of data (GB) scanned ?

Nor do you say what CPU you have or how closely this system is to the others, in respect of all of the above and CPU, etc ?

Nor do you say if this was a first scan which is likely to take longer than subsequent scans ?

Nor do you say if you have any other security software installed that might impact on the avast scan ?

This is a scan that I have just run, see my signature for my system specs:
Quote
* avast! Scan Report
*
* Scan name: Full system scan
* Started on: Monday, April 05, 2010 3:44:45 AM
* VPS: 100404-0, 04/04/2010
*
Infected files: 0
Total files: 60123
Total folders: 4022
Total size: 9.4 GB
*
* Scan stopped: 05 April 2010 03:48:28
* Run-time was 3 minute(s), 43 second(s)

So that scan is about 1/3 of the files scanned on yours, which can't really be compared, but as you can see mine is pretty quick for the Full System Scan.
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Offline marc-d-l

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Re: Avast so slow scaning
« Reply #2 on: April 05, 2010, 06:40:11 AM »
I ran a full scan no pups took 1hour and 37 minutes. tested files 178077 data tested 35.81
the longest scan time I have had before now was 48 min. Seems to me that this is an extreem long time
I can get a quicker scan with just about any other AV .
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Offline DavidR

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Re: Avast so slow scaning
« Reply #3 on: April 05, 2010, 04:00:25 PM »
Sorry but there are still many questions unanswered.

You say the longest scan you had before was 48 minutes, but don't give any information about it either.

The problem when considering your comment "I can get a quicker scan with just about any other AV" there is no direct way to compare that either as we don't know what the other scan settings are and that would just be comparing apples with oranges.

That was why I showed the scan info and image for a full system scan on my system, allied with my system information in my signature.

Now your scan isn't anywhere near close to the speed I'm getting on what is a reasonably good system about a year and three quarters old. So it is no speed freak.
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Offline Hally

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Re: Avast so slow scaning
« Reply #4 on: April 05, 2010, 06:36:20 PM »
Hi  :)

1) Have you changed any scan settings in Avast .. In between the 48 minute scan - & - The last scan that took 1 hour 37 minutes?

2) During the scan that took 1 hour 37 minutes .. Did you continue to use the computer while Avast was scanning?

Full Scan with Avast 5 on my computers ( For approx 70 GB to 80 GB ) takes about... 1 hour 15 minutes - to - 1 hour 30 minutes.

Hally
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Offline wonderwrench

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Re: Avast so slow scaning
« Reply #5 on: April 06, 2010, 05:59:49 AM »
I read this post and had to test this my self. Doing a full scan with pups turned on, not using the persistent cache but building one. All other options on default here are my results. Using Avast 5 Free on the rig in my sig.
Time:   27m50s
files:    287,784
folders: 69376
data:    309.77 gigs

That is lightning fast if you ask me. I will test my old laptop running XP and report.
« Last Edit: April 06, 2010, 06:53:25 AM by wonderwrench »
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Offline wonderwrench

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Re: Avast so slow scaning
« Reply #6 on: April 07, 2010, 01:27:55 AM »
I got a chance to run a full scan on my laptop, Windows XP pro sp3 32 bit, Intel 1.4 ghz Centrino with 768 megs of ram and a 5400 rpm 60 gig hard drive.
I'd say scan speed suffers badly compared to the system in my sig. Who'd of thought. CPU usage averages 60-80% during the scan. DCP latency is in the green. The system is usable during the scan but I sure would not try and watch video or even play an mp3. Used "full scan" default settings plus pups.

time: 58:54
files: 78663
folders: 5153
data: 32.71 gigs

I then unchecked the setting for building the persistent cache and re ran the scan.
CPU usage averages less than 10% with some spikes to 40/50%

time:19:49
files: 78900
folders: 5137
data:  32.90 gigs

I then checked the setting to use the persistent cache and ran the scan again.
CPU usage is about the same as the test above.

time:10:28
files: 78717
folders: 5136
data:  32.77 gigs

So far I gather that building the persistent cache is rather CPU intensive.
So much so that it may be best to turn it off on low end hardware or enable using
the cache so subsequent scans are faster. I need to run one more test with the
cache building back on and see what happens. I will report back!


« Last Edit: April 07, 2010, 04:06:30 AM by wonderwrench »
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Offline wonderwrench

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Re: Avast so slow scaning
« Reply #7 on: April 07, 2010, 04:52:28 AM »
Ok I ran another full scan with cache building enabled still using the persistent cache. The results looked just like the first test.
To be sure I re-ran the test one more time and  go the same results. 58 minutes to scan and high CPU usage. The reason for building
a persistent cache is to allow future scans to be completed faster. This does not seem to be the case, at least on low end
hardware. The persistent cache is also used by the real time shield. Disabling the building of the cache could cause performance
problems with the real time shield but I have no solid evidence of this. The real time shield would be scanning more
files for sure. There is a problem that needs a fix. Either the engine that builds the cache needs to be tuned better or building the
cache should be disabled by default in manual scans either on low end hardware or all harware.

IMO for the time being people with complaints of slow scanning should be disabling the building of the persistent cache for manual scans.
Keep in mind this could cause other performance issues I have not tested for. Yet!
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Offline DavidR

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Re: Avast so slow scaning
« Reply #8 on: April 07, 2010, 05:07:40 AM »
There is obviously going to be a limit as to how fast it can get, once the persistent cache has been fully populated you will have achieved the highest optimisation.

You may also notice that if you regularly defrag/optimise your hard disk the first scan after the defrag will take longer.

I can't recall what the default settings were offhand, but I do believe that 'Store data about scanned files in the persistent cache,' is not enabled by default. I say this because I believe I recall enabling it for the Quick and Full System Scans.

Looking at a Scan that I haven't used/tested the Select folders to scan, Expert Settings, Performance, doesn't show the 'Store data about scanned files in the persistent cache,' so I don't know if this is what you mean by building the persistent cache. As it says in the settings enabling this option will slow down the scan.
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Offline wonderwrench

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Re: Avast so slow scaning
« Reply #9 on: April 07, 2010, 11:24:12 AM »
There is obviously going to be a limit as to how fast it can get, once the persistent cache has been fully populated you will have achieved the highest optimisation.

You may also notice that if you regularly defrag/optimise your hard disk the first scan after the defrag will take longer.

I can't recall what the default settings were offhand, but I do believe that 'Store data about scanned files in the persistent cache,' is not enabled by default. I say this because I believe I recall enabling it for the Quick and Full System Scans.

Looking at a Scan that I haven't used/tested the Select folders to scan, Expert Settings, Performance, doesn't show the 'Store data about scanned files in the persistent cache,' so I don't know if this is what you mean by building the persistent cache. As it says in the settings enabling this option will slow down the scan.
I think I see what you are saying. I understand how the persistent cache is intended to work. I question if it works correctly. I defrag my drives like most people wash there hands. Yes it sure would be nice if there was a reset to default button would it not. I'm quite sure building the persistent cache is enabled by default on a full scan but like you say anything is possible. It sounds like it should be to me. The question is with the huge performance hit on older lower end PC' should it ever be on. Plain and simple Avast 5's scan speed with the option to build the persistent cash on low end systems is a problem. Many Antivirus programs use a similar cache system so subsequent passes are actually faster in real life not 3 times slower.

Maximum PC just did a review on 10 security programs. The review states "Avast 5 Internet security had the slowest scan engine out of the 10 products tested". "It also allowed a dirty archive to be downloaded and failed to detect any of the infected files within". Avast 5 Internet security received a 5 out of 10. Only one product was rated lower. Their testing is far from scientific so I wonder about the validity of the testing. The failed detection I'll forget about but the scan time is a problem. If I had 300 gigs of data on my laptop it would not be scanable as it would take about 10 hrs. Maximum PC has a large subscriber base so if I was ALWIL I'd be getting in touch with Maximum PC and see whats up. Their review does not even mention Avast in the end. Its like nope in the ash can.

I'm going to test more on the rig in my sig and see how much affect building the persistent cache has on it. Not that I need to scan faster but is building the persistent cache slowing scanning a measurable amount. Whats funny about my previous tests on my laptop is the scan is slow when both, using the persistent cache and building persistent cache are enabled. It seems using the persistent cache does not improve scan time even after repeated runs.
If its not going to shorten scan times what good is it in the first place.
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Offline DavidR

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Re: Avast so slow scaning
« Reply #10 on: April 07, 2010, 03:36:59 PM »
When you talk of performance hits on old systems, avast has always tried to get the balance right in the default settings, particularly in regard to performance Vs protection and that is why I feel they would have left that element unchecked.

More so in the Quick Scan as that really is all most should need to do on a regular basic, it is what I do weekly, and that I have also set to Store data about scanned files in the persistent cache and this I'm sure wasn't the case in the default setting.

I normally only run a full system scan when people mention it here that they are experiencing problems and I do that whilst responding to posts.

Dirty archives or clean ones are inert, so why would that be an issue, whilst they should be scanned by the web shield they aren't by the file system shield because they have to be opened, extracted and run and before that happens the executables, etc. would be scanned. Not knowing anything about there testing or settings, I can't comment further and have no intention of wasting any further time on it as it is also diverting the original topic.

Unfortunately there is no Reset Defaults button in avast, something which several of us have been calling for for ages as there are people that are never done tweaking their system to within an inch of its life and haven't a clue what the defaults were manually reset.
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Offline wonderwrench

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Re: Avast so slow scaning
« Reply #11 on: April 07, 2010, 11:57:11 PM »
I ran a full scan on the rig in my sig today with building persistent cache enabled.

time 28:47
files 228332
folders 69471
size 309.83 gigs

I then enabled the use of the persistent cache and re-ran the full scan

time 9:21
files 288233
folders 69471
size 307.75

So it looks like using the persistent cache really speeds up the scan on higher end hardware, not that its needed. On lower end hardware it does nothing  because the overhead in building the persistent cache is higher than benefit of using the cache. So my final thoughts are if you think scanning takes too long disable the building of the persistent cache and be done with it. ALWIL should really change the default setting to not build the persistent cache by default. AV review sites and users a like will be much happier. The cache is made to speed up scanning but on lower end hardware it does the opposite.
On higher end hardware its not needed in the first place. Is it needed at all? Maybe for the realtime shield.
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Offline wonderwrench

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Re: Avast so slow scaning
« Reply #12 on: April 08, 2010, 08:09:50 PM »
Update: I did a clean install of Windows 7 Ult 64 bit on the rig in my sig last night. After installing Avast 5 Free I had a look and the full scan is set to build the persistent cache by default as I first thought. IMHO this needs to change ASAP! The best fixed would be to improve the engine that builds the persistent cache to a point that its no longer a probelm. If this is not possible the best solution would be to disable building the persistent cache on low end hardware by default. At a minimum disable the persistent cache on all installs by default.
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Offline DavidR

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Re: Avast so slow scaning
« Reply #13 on: April 08, 2010, 08:28:08 PM »
I really don't understand the term you use, "the full scan is set to build the persistent cache by default as I first thought."

Have you got a screen shot of those settings ?
See my image (Full Scan, Settings), the setting highlighted (the one I manually set), is what I would consider set to build, or as it says in the note for the option "This option tells the engine to 'populate' the persistent cache during the scan."

The other one just tells it to consult the persistent cache before scanning, if however the persistent cache isn't being populated (built) this wouldn't be building any cache.

So as I said I don't know which one you are talking about.
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Offline wonderwrench

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Re: Avast so slow scaning
« Reply #14 on: April 09, 2010, 12:27:58 AM »
I really don't understand the term you use, "the full scan is set to build the persistent cache by default as I first thought."

Have you got a screen shot of those settings ?
See my image (Full Scan, Settings), the setting highlighted (the one I manually set), is what I would consider set to build, or as it says in the note for the option "This option tells the engine to 'populate' the persistent cache during the scan."

The other one just tells it to consult the persistent cache before scanning, if however the persistent cache isn't being populated (built) this wouldn't be building any cache.

So as I said I don't know which one you are talking about.

Yes the bottom choice is enabled (checked by default) in the Full Scan settings. The top one is not. Build, store or populate its the same thing.
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