Author Topic: Clearing the Persistent Cache?  (Read 27410 times)

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Offline Lisandro

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Re: Clearing the Persistent Cache?
« Reply #15 on: February 17, 2010, 10:36:56 PM »
What are the principles of "trusting"?
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Quick checksum of the file into the whitelist.
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ioyuioynx

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Re: Clearing the Persistent Cache?
« Reply #16 on: February 17, 2010, 11:17:23 PM »
Consider date created, date modified, and the checksum of the file.  All these should be considered to check if the file has been modified.  If any of these have changed, then the contents of the file would be scanned.

So when Avast is doing active scans of files being used, does it compare Windows trusted files all the time? I mean, without some sort of check, how does it know that the file hasn't changed compared to whats in the whitelist. How much quicker is this check than if that file was to be scanned?

olddog

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Re: Clearing the Persistent Cache?
« Reply #17 on: February 18, 2010, 05:08:44 AM »
...How much quicker is this check than if that file was to be scanned?

That would depend on exactly what check is made compared to how long it would take to scan the file, and in turn how big the file is.

ioyuioynx

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Re: Clearing the Persistent Cache?
« Reply #18 on: February 18, 2010, 08:46:25 AM »
...How much quicker is this check than if that file was to be scanned?

That would depend on exactly what check is made compared to how long it would take to scan the file, and in turn how big the file is.

Well, exactly what check needs to be done to a file to see if it has changed. That check.

saanvi

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Re: Clearing the Persistent Cache?
« Reply #19 on: February 18, 2010, 11:32:04 AM »
Digital signature.
Quick checksum of the file into the whitelist.
Thanks for your answer. It seems Avast! to be the fastest antivir now. :)

Offline Lisandro

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Re: Clearing the Persistent Cache?
« Reply #20 on: February 18, 2010, 11:35:28 AM »
So when Avast is doing active scans of files being used, does it compare Windows trusted files all the time? I mean, without some sort of check, how does it know that the file hasn't changed compared to whats in the whitelist. How much quicker is this check than if that file was to be scanned?
I've answered that before... the white list is safely populated. The check is faster than the rescan (otherwise, the feature won't be of any help, will it?).
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Offline Gopher John

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Re: Clearing the Persistent Cache?
« Reply #21 on: February 18, 2010, 03:52:16 PM »
One example of the difference would be the scan logs.

My first full scan(on January 27) before populating the persistent cache took 48min 44sec to scan 51.26GB while my latest full scan took 17min 38sec to scan 49.03GB.  In between these scans I'd updated some programs as well as the MS updates on Patch Tuesday which required those to be rescanned during the last scan.  The reduction from 51.26 to 49.03GB was due to deleting a couple of installer files and running CCleaner to remove all the temporary files that had accumulated.

This is only an example, and during normal usage the variance would be different, so cannot be directly compared.  Obviously, there were quite a few files that had been changed by the various OS and program updates that required rescanning of the contents but the majority of the files had been unchanged and only required verification that there was no change.

I have no way to determine which files were content scanned and which files were just checked for updates via persistent cache, nor how exactly that affected the scan time, nor do I care.  Obviously, it's above my pay grade. ;D
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Offline MikeBCda

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Re: Clearing the Persistent Cache?
« Reply #22 on: February 18, 2010, 07:43:49 PM »
I'd posted somewhere else here that I'd seen a huge speed increase by ticking both cache options.  Back on 4.8, I was scanning about 6 gigs (with archives excluded) in roughly 15 minutes.  My first full system scan in 5 (with packer settings left at default, by the way) took just under an hour, obviously due to having to populate the persistent cache from scratch.  The next scan with same settings, a week later, took about 8 minutes -- roughly twice as fast as 4.8 without archive scanning.
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mantra

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Re: Clearing the Persistent Cache?
« Reply #23 on: February 22, 2011, 04:12:25 PM »
The persistent cache is indeed stored in the db*.dat files (there's one file per volume).
Typically, they shouldn't be bigger than a few hundred KBs.

Thanks
Vlk
thanks
where are these files in w7 ?
but should i stop the service and avast pop to fix now ???
i guess i should detele some reg keys ,right , to purge the persistent cache and re-build
i want to have a persisten cache only for 1 volume
yesterday i did for all my volumes 6
« Last Edit: February 22, 2011, 04:17:04 PM by mantra »

Hermite15

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Re: Clearing the Persistent Cache?
« Reply #24 on: February 22, 2011, 04:27:20 PM »
thread is more than a year old, start a new one.

edit: hmm... no need, there's no solution to your problem, just disable the persistence cache if you fear the indexing of some sort of content ;D

ps: you're a real Avast reverend ???  :D
« Last Edit: February 22, 2011, 04:29:44 PM by Logos »