Win 7 64bit Avast Free 2015.10.2.2214 (very recent update) Laptop with a 5400 RPM drive.
I am experiencing constant intense disk writes to lscache.dat (Using Win 7’s Resource monitor. I don’t notice any unusual reads. Over 29,000,000 B/sec per Win 7’s resource monitor
If I disable File System Shield this intense activity stops.
Any suggestions?
What’s filesize of this file? Can you please compress it and send it to kurtin@avast.com? Thanks.
I have emailed you a zip of the file and a screen capture of Win 7’s Resource monitor showing the high disk write activity. It is slowing my system dramatically so, at the present, I am toggling off File Shield when I am not doing anything needing it. Note, turning off any other shield has no effect.
I always have a little system idle activity but this is extreme and I am not exactly certain when it stated, I believed it was when I upgraded to 2015.10.2.2214. My HD activity LED is not that well placed 
Possible cause, now my system is running normally.
I tried changing a number of changes to Avast AV, reset defaults, reinstalled.
The problem is gone, I suspect I had a corrupt or too huge lscache.dat. I tried disabling temp ad permanent caching, rebooted, then enabled them again and rebooted. Writes to lscache.dat activity started at a much lower level and eventually fell to near zero. I note no unusual disk activity now. Hope it stays that way 
I believe over 2+ years of system changes/updates and AVast updates, possibly lscache.dat became corrupt or overloaded with old garbage. lscache.dat WAS 3.6MB! It is 1KB now!!! It likely will grow with as I use the computer or do a full scan.
Perhaps resetting lscache.dat when Avast is updated or an option to reset it directly would be handy. This, of course, assumes I found the problem - a corrupt lscache.dat. 8)
I have the same symptoms: intense disk activities, only for lscache.dat. The problem stops when I disable all AVAST shields.
I found neither restoring defaults or uninstalling/re installing Avast solves the problem. In my case, neither removed the cache data or other files. It would seem uninstall should be complete and restoring defaults should be complete.
My previously posted solution worked for me. Possibly the
avast! Removal Tool - avast! Uninstaller
https://avast-removal-tool.com/
states it will fully uninstall AVAST so a fresh install works. I didn’t try it (you must run it in safe mode) so I do not know if it really deletes all content Avast puts in /ProgramData.
At any rate, it certainly seems a corrupt lscache.dat was my problem.
Note, when I finally reset lscache.dat It started with much lower but significant activity which essentially went to zero as it cached the files my computer commonly accesses. I presume that was because it was consulting the in memory temporary cache.
It would appear Avast could easily address this apparent bug.
I found the solution hopefully. It was helpful that you stated, that only File Shield causes this. Uncheck the transient caching in File Shield settings (Click Customize).
Avast has included a very bad feature with bugs in it. It can destroy the HDD cycles rapidly. After doing this my HDD light stays super calm. You can also check you HDD activity in Resource Monitor ( type “perform /res” in Start menu). Glad that I caught this issue quickly and that too for your thread. 
Interesting, since the file written to is the permanent lscache.dat, not the transient memory cache.
This I/O activity stress any hard disk, grossly slows any system and clearly will destroy a SSD quickly.
A dangerous bug for sure!
Thought that transient works every time we reboot and permanent is for previously checked files. Anyways unchecking both can produce any result or no result. If not for the bug, then this bad feature would have been pretty cool from avast.
Sure a nightmare for SSDs (as they will never know abt it for its speed :P)
I have had the same problem today with Avast free build 2215 under Windows 8.1-64.
After an hour of tries, I found an easy solution:
. restart in safe mode
. delete file (lscache.dat)
. restart
I hope that can help.
Can confirm I’m also having this problem. After a deal of browsing the web, I shut off my browser and around 400,000B/s is being written to lscache.dat, my LED is constantly blinking for around a minute. How do I get this to stop?
It never did this in previous versions.
Still having this issue of high disk activity. Strange behavior … seems to always write around 400,000/600,000B/s to lscache.dat after clearing my cache in internet browser or simply just when closing the browser. Turning off transient/permenant cache option doesn’t change anything.
It doesn’t read when I turn off the File Shield and clean the cache but when I turn it back on after clearing the cache, the high disk activity resumes the moment I reactivate it.
Is this even normal behavior…? Cause I don’t remember this happening in previous versions of avast at all… whenever this happens my LED on my pc goes crazy for around a minute. Is this a bug? Can I get some sort of answer from a dev or something please? Even if it’s just to say this is normal?
Hello,
we are working on this issue, it should be fixed in next SP the latest.
Thanks,
B.
Thanks for the response. A reply here when the fix is working would be appreciated.
i recently had a high disk activity issue with v2215 and tracked it down to the software updater module. I disabled this and wham…problem solved. Wonder if this is related to what you guys are discussing here?
Software (Program) updates are set to manual by default.
VPS (Virus data base) updates are on by default as they should be to keep your protection
against the newest discovered viruses as up to date a s possible. (streaming updates)
Hi Bob3160. See my response https://forum.avast.com/index.php?topic=168703.msg1200471#msg1200471
So you’ve removed the Software Updater Scan. It’s an optional tool not really part of the AV program.
Unfortunately not, for me. I never install the Software Updater module for Avast!, I mostly just install the Shield Protection and nothing more. I feel the other features are just a waste of space. I’m still having the problem with just the Shields installed.
So what sort of compensation will we get for the damage it has done to our SSDs over the past week???
This has been hammering my SSD with 70MB sec writing for the past few days, managed to stop it after 2215 update and settings/ tools and disabling all tools and then re-enabling them.
I expect better from Avast and I would have expected you to tell us to roll the software back a version to stop this damage if that would have fixed it temporarily.