Avast Quick Scan is slower than before

[CaSPeRr]

Hi I have Avast Internet Security 5.0.

When I did my first couple of quick scans it completed the scan in 8 minutes and the speed it was scanning data was approx 110MB and around 50MB when it reached the end.

Now when I do any scan be it quick or full it reads data at 2/5MB a sec and takes over 2 hours to complete.

I have a complete new Vista install. and there is nothing else installed or stored apart from complete Vista Updates and Avast with complete updates

Any explanation for this?

[Vlk]

It will be the effect of the Persistent cache.
Please run the Full System Scan at least once to populate the cache; after doing so, all subsequent scans should be fast again.

Thanks
vlk

[CaSPeRr]

Hi I have done a couple more full system scan and they are all slow.

I then installed a fresh version of Vista again and now the results are

Quick Scan - Data Scanned 10GB - Scan Time 50 Seconds

Full Scan - Data Scanned 22GB - Scan Time 8 Minutes

Custom Scan Everthing Selected- Scan Time 18 Minutes

It seems to be working fine. The only thing I did last time was DEFRAG the Hard Drive.

I have been informed to do a few full scans so that Avast can populate the cache.

Is there any known issues that affect the cache and slow down Avast Scanning speed after defrag?

[Lisandro]

Is there any known issues that affect the cache and slow down Avast Scanning speed after defrag?

On contrary, defrag should increase (or, at least, not affect) the scanning speed.

Also: http://blog.avast.com/2010/04/25/how-to-make-the-full-system-scan-6x-faster-in-10-days

[CaSPeRr]

Is there any known issues that affect the cache and slow down Avast Scanning speed after defrag?

On contrary, defrag should increase (or, at least, not affect) the scanning speed.

Also: http://blog.avast.com/2010/04/25/how-to-make-the-full-system-scan-6x-faster-in-10-days

I have set the computer to Defrag the HD, I will post the affect it has had regarding the scanning speed.

[DavidR]

I don't know if in the act of defragging your system the files are no longer in the same location and if that is tied to the persistent cache, then my guess would be that the persistent cache would need to be updated.

I do notice that after a defrag the first scan is a little slower, not anything like what you experienced. So I don't know if your partition was heavily fragmented, mine I regularly defrag it so there wouldn't be much of a change. After running the full system scan a couple of times it is back to normal, very fast.

[CaSPeRr]

I don't know if in the act of defragging your system the files are no longer in the same location and if that is tied to the persistent cache, then my guess would be that the persistent cache would need to be updated.

I do notice that after a defrag the first scan is a little slower, not anything like what you experienced. So I don't know if your partition was heavily fragmented, mine I regularly defrag it so there wouldn't be much of a change. After running the full system scan a couple of times it is back to normal, very fast.

I was thinking the same. When I analysed the HD with Defrag the files are all over the place. After Defrag the HD looked better but Avast was slow.

Im not sure if Avast persistent cache loses the location(its techincal) after the files have been rearranged.

After a fresh install of Vista Avast is behaving like it should. I have set the computer to defrag. Will let you know if Avast slows down.

Can anyone from the DEV shed some light on if persistent cache can be affected by defrag?

[Asyn]

It seems this slowdown doesn't happen with FAT32.
Are you all using NTFS..??
asyn

[Lisandro]

I don't know if in the act of defragging your system the files are no longer in the same location and if that is tied to the persistent cache

As far I know, persistent cache has nothing to do with low level allocation files (clusters).

[igor]

Well, it doesn't have anything to do with clusters - but the persistent cache works on NTFS drives only.
Though I don't know what "slowdown" Asyn is referring to exactly... (being it his first post in this thread)?

[Asyn]

Well, it doesn't have anything to do with clusters - but the persistent cache works on NTFS drives only.
Though I don't know what "slowdown" Asyn is referring to exactly... (being it his first post in this thread)?

I was trying to reproduce (defrag/scan) the problem but didn't run into any slowdown on this machine.
But as I'm using FAT32 here your answer above says it all.
asyn

[DavidR]

I don't know if in the act of defragging your system the files are no longer in the same location and if that is tied to the persistent cache

As far I know, persistent cache has nothing to do with low level allocation files (clusters).

I just know that after a defrag the scan is a little slower, why I leave to those that can better explain why.

[CaSPeRr]

I have done defrag 4 times and after each defrag the scan gets slower.

My 1st custom scan took 18 minutes.

The next one took 35 minutes

The next one took 28 minutes.

The next one took 25 minutes.

Approx Data is around 22GB.

Defrag only takes 10 minutes to complete now.

I will do 2 more custom scans without defrag and post the results here. I expect it to eventually get under 15 minutes. I will post the results when I have them. I also created a notepad scan log. There are many Files it cannot scan or access denied. Im assuming they are Windows System Files. Is there anyway to scan them?

Also I have ticked check for PUP and ALL FILES on every Real Time Shield.

I opened the notepad log Avast created and it was 50MB but took ages to open. I beleive Avast was scanning the file before opennig. I guess someone did say to me that it would bring the system down and it has.

Which option/setting have I selected and need to deselect?

[DavidR]

Please post some common examples of the file names and locations that can't be scanned.

If these are permissions or password issues, the simple answer is no, there is nothing you can do if you the user haven't got permission to access an area (short of running the scan from a user account who has permission).

Well by default the .log/.txt files aren't scanned (as they are in effect inert), unless you have gone into paranoid settings, bumping up Sensitivity to High, Test whole files, etc. etc. as that could have the impact on performance you mention delay in opening large files, more so when you add scan for PUPs also.