OK, I just did a Full System Scan with the latest version of Avast! and i just CAN’T BELIEVE how fast was that done. Is scanned my whole harddisk (about 300 GB of data), with no exceptions, I even hardened the scan (all packers etc.) in about 10 minutes. The old Avast! 4.8 always needed A FEW HOURS to scan my whole harddisk. I simply can’t understand how is that possible!
Note: I have also completly disabled the Persistent cache function.
Please comment. Thank you! 
Is there an Avast 5 tweak guide of some sorts anywhere on the internet? The built-in help file is not enough, it doesn’t explain everything. I’m looking for the best combination of security and safety.
You obviously have the fastest computer in the world.
I ran a test scan like yours and here are my results"
Run Time 1:19:32
Tested Files 82977
Tested Folders 5922
Amount of Data Tested 22.22GB
My computer has a 3.2G CPU and 2G of RAM. Time to throw it away. ;D
I have also completly disabled the Persistent cache function.
: i think this the reason of lightning speed just like skimming ;D
Regards!
I think it’s better to create a “custom scan”!
Only in this case, you can really make a full and deep scan of your system.
But the settings must be correct to do that!
Try it, you’ll see… 
I’d love to try it, but please tell me how to set all the options to get the really thorough scan.
I installed the german version.
Because of that, I don’t know the notions in your version. Sorry!
But I think, it’s really easy to find the right settings.
Just try a little bit and let scan the whole things you can.
This scan will be deeper, but also longer.
I did it in this way, too.
Perhaps here is another forum-member who can explain it more exactly.
Good luck!
There is no way for Avast or any other scanner out there to scan an amount of 300Gb in 10 minutes! ???
…Time for Guinness Book ;D ;D
With the previous version of Avast gave us 4 hours to scan a 40Gb file at a speed close to 10Mb / s, if I remember correctly the version prior to 5.0.504 and 4.8 were also much faster but perhaps control was less effective! however is the fact that a scan of 4 hours is not just the PC especially those who may use it to work also because very often when scanning normal use of the computer is slow and not a little
Thank you all for the replys, but I still don’t know how to set the settings so that I will have the best protection and most thorough scanning. Should I post my Avast.ini file?
It takes 6 hours to scan my system even with the new Avast 5. I do have 2 hard drives, however, even something small like yours should take longer than 10 minutes.
I was surprised also with the Full System Scan. With AVG it took 10-12 hours to scan my PC. Way less with Avast. One reason for short scan times would be if the user set any Exclusions, but the default is no Exclusions.
Something I find strange is that if you make a custom scan, there is a checkbox “Scan All Files”. If you don’t check that, what in heck is being checked? Perhaps the same applies to the Full System Scan - maybe non-infectable files are being skipped. There is nothing in Help about what is in the Full System Scan.
For custom scans, selecting “content” implies all files are checked. Selecting “name extension” is exe, bat, com etc. Those explanations are clear but do you have to check the checkbox too? What if you don’t?
I created a custom scan and now it’s scanning properly (slow and thorough).
Is there any way I can remove Quick and Full scan from the Scan Now tab? I won’t be using them.
I have unchecked all the Persistence Cache options, I don’t use that at all. Is that OK?
Thank you!
That is my interpretation also as only files that present an immediate threat and not inert files. However here is a bit from the help file. See highlighted text, which is the relevant bit.
[b]Full System Scan[/b] - This performs a more detailed scan of all your computer's hard disks and by default, all files are scanned according to their content, in other words, avast! looks inside every file to determine what type of file it is and whether it should be scanned. The whole file is tested, not just those parts of the file at the beginning or at the end where infections are normally found.
See image of the Custom scan settings, whilst it doesn’t mention selecting All files, by default the setting is set to Content, so all files within the selected areas would be checked by content and scanned accordingly.
Personally I use the Quick scan weekly (it covers those files most at risk, the boot partition, memory scan and startup items. I don’t feel the need to go ballistic with on-demand scans when the essence of avast is its resident protection. I occasionally run a Full Scan and that I feel for me is more than enough.
I don’t believe that you can remove the default scan options from the list.
I can’t see the reason for changing the Persistent cache settings form the defaults (you may not remember how they were set if you want to return to those defaults) and their purpose is to speed up the scan without placing any additional risk by not scanning certain files that haven’t changed since the last scan. Personally I would have asked the question “Is that OK?” before making any change.
OK, my custom scan finished and needed over 4 hours to scan 300 GB data. Not that’s more real I think (compared to my first post). So I will be using this custom scan from time to time and depend on the resident protection and other layers of protection. The other important thing to me is the Windows Explorer context menu scan, I hope I set it right, I use that one a lot. About persistent cache: the 4.8 version didn’t use that function, as far as I know, and it was alright. I don’t mind a slower scan if it’s more thorough - so I guess won’t use persistent cache. Thank you all.
And I have to say that Avast! 5 is great!
That’s correct 4.8 had no persistent caching function so it ‘couldn’t use it,’ but that doesn’t mean it was all right.
The whole point of the persistent cache has nothing to do with the thoroughness of any scan, but to avoid the pointless scanning of files that haven’t changed since your last scan. Only certain files are considered for inclusion in the persistent cache, those MS files with digital signatures and other whitlisted files from other applications, etc. After the first time they have been scanned they would be included in the cache if you enabled that function.
This is all to do with the constant screaming out by users for faster scanning speed.