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Why, when I'm doing nothing at all, will my hard disk suddenly start thrashing?

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Summary: There are several reasons you might see hard disk activity when you're not doing something yourself. It's not hard to see what's causing it.

Why, when I'm doing nothing at all, will my hard disk suddenly start thrashing?

It could be for many reasons. The most common are anti-virus tools or the system indexing service if it's enabled.

To find out what's happening on your system, we'll use a filesystem monitoring tool. Download FileMon from the folks over at Sysinternals.com. It works on Windows 95 or later, and Windows NT 4 or later.

When you run FileMon you'll probably be surprized at how much your system is already doing while you're not doing anything. As long as the disk isn't thrashing (it's possible that it's not even being hit at this point), it's all quite normal. Let FileMon run.

As soon as you hear your hard disk thrashing when you think it shouldn't be, press CTRL+E in FileMon to stop the capture. The last few screens should be full of disk access by the offending application.

What we may determine is that this is expected behaviour for your system. However we might also decide that whatever is running is unwanted, and we'll work through the steps to turn it off or remove it.

Article C1828 - August 10, 2003

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Recent Comments
14 Comments

Have you emptied your recycle bin? This article may also help: http://ask-leo.com/how_can_i_tell_whats_taking_up_so_much_disk_space.html

Posted by: Leo at February 14, 2006 8:52 AM

Nicely done Leo. Systm restore was using a LOT of resources. All is quiet now...

Thanks,

P.

Posted by: Peter at March 3, 2006 4:39 AM

Hello Leo & Everyone

My hard disk has started thrashing whenever Outlook 2003 has been running on idle for a few minutes. If I close Outlook 2003 the disk stops thrashing.

I tried FileMon and captured the screen as soon as the thrashing started - it was full of the line "OUTLOOK.EXE:2144"

The machine is running Windows 2000 Pro with Service Pack 4. It has 1.5Gb of RAM and the hard drive is a 123Gb IBM. Can anyone help me?

Many thanks

Simon.

Posted by: Simon at April 7, 2006 5:10 PM

Actually, try letting it "thrash" for a while. Outlook compacts its PST file in the background at idle time. At some point the file will have been compacted, and the thrashing should stop. (And technically it's not thrashing ... unless it somehow impacts your ability to do other things.) Conversely you could force compaction and see if that makes the thrashing stop as well.

Posted by: Leo at April 9, 2006 12:05 PM

Hello Leo,
My laptop has been thrashing the HD, Also MS WORD won't open and after it tries it leaves a rectangle of screen that does not repaint on the desktop also Norton Internet security 2006 does not open. I have phoned Symantec and run SYMNRT.exe and reinstalled Norton Internet security 2006 and reinstalled Norton Ghost 10 and reinstalled Word 2003 pro but I am right back at the starting point. Ctl Alt Del does not shut the computer down so I have to manually shut it down. The last time I restarted the laptop the screen was black so I manually shutdown again, after leaving the laptop shutdown for an hour I restarted it and it opened fine but the above problems are still there any help appreciated.
My laptop specs are
990 Megabytes Installed Memory, Slot 'U5' has 512 MB, Slot 'U6' has 512, Windows XP Professional Service Pack 2 (build 2600), 2.67 gigahertz Intel Pentium 4, 8 kilobyte primary memory, cache, 512 kilobyte secondary memory cache, 40.00 Gigabytes Usable Hard Drive Capacity, 26.93 Gigabytes Hard Drive Free Space, SiS M650 [Display adapter]Default Monitor,

Posted by: Andrew Goodall at April 18, 2006 3:41 AM

I believe it is Norton Antivirus 2006 Autoupdate program that is stuck and is causing problems. Symantec who own the product won't help find the answer without a 39.95 Euro charge and suggested I contact a local engineer to get my problem sorted. Any help appreciated...

Posted by: Andrew Goodall at April 27, 2006 1:46 AM

If your machine is tweaked to perfection, and you have not disabled optimise hard drive on idle, and you have smallish clusters and or lots of data on your drives, defrag hangs.

Norton 2006, Outlook cleanup, Outlook Express Cleanup, Scheduled Disk Doctor defragmenting, Viruses and Spyware also do create the same disk slow scenario.

Personally, I disable deframgenting when idle, format my drives with 64K clusters (lose a bit of space but pickup loads of disk speed), and defrag via bat file on startup.

It's a good idea to disable system restore on non essential drives. I actually don't use it, as my OS is installed on a partition, and Documents and Settings and data files are on another, that is backed up. On system failure, I reinstall the OS and programs, do some registry tweaks, and point my data files to certain folders, and I'm back in business.

I've had so many problems with Windows on our network the past month. Viruses have been on the increase. I'm moving some machines over to Linux and running Windows in a virtual machine for certain applications. I will still however need a single Windows dedicated machine for certain software.

Posted by: Cec at August 29, 2006 3:21 PM

All the above suggestions are 'over my head' so, I guess I will have to listen to the growling that is called thrashing by the literate above. I, too, wonder if this is taking up disk space which seems to be decreasing as time goes by and I do not add downloads or new programs. Defrag.,scanned often.

Posted by: Anne Dakmak at March 10, 2007 2:37 PM

To stop thrashing hard drive in Windows XP, alter the setting of memory from the default (adjust for best performance of programs) to 'adjust for best performance of system cache'. There are no bad side effects.

Posted by: James Baring at March 15, 2007 5:47 AM

I ran process monitor on my wife's computer because its HD keeps running even though I have shut off indexing and defrag. It has hundreds of entries where snippit is opened and closed. She doesn't even know what snippit is. I do use it on my computer and have months ago on hers. Is it likely that there is some sort of key logging or similar spy process going on?

Posted by: John P. Brown at April 21, 2009 12:20 PM

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