A question long hasn't being asked.

I have this question since the XP days and haven't ask this. Don't know if anyone knows the answer. So, since XP SP2 or maybe earlier, they have Windows Update feature. And I can use automatic download before install it. And this is the strange part. Every time it is downloading Windows Update, my HDD is clicking like mad, which is not normal. I can download much larger data without my HDD clicking mad. Usually they cache the data in RAM for a bit and do a continuous write which HDD won't click at all.

So, why downloading Windows Update makes my HDD clicking mad and slow?

I noticed that on my work computer here running Windows 7 64 bit. If Windows Update was downloading 500MB of stuff my computer would slow to an almost unusable crawl. Not sure why and IT couldn't figure it out.

But now we run a Windows Update Server, so stuff gets pushed once a week to workstations, so I don't have that issue anymore.

I don't think I've ever seen any unusual slowdowns while WU is doing its thing.

3 hours ago, Harlequin wrote

I noticed that on my work computer here running Windows 7 64 bit. If Windows Update was downloading 500MB of stuff my computer would slow to an almost unusable crawl. Not sure why and IT couldn't figure it out.

But now we run a Windows Update Server, so stuff gets pushed once a week to workstations, so I don't have that issue anymore.

If you have an old disk and you're using more memory than you probably should be, then Windows Update's writes to the disk start starving the pagefile. This means that background apps (like explorer and the taskbar and all of the system services including the ones that do things like the clipboard and window composition) which have their pages pushed out to the pagefile to let your memory hungry foreground apps (like Visual Studio) consume more virtual RAM than your physical hardware should really allow. The problem is that when that background app wants their memory back the thread has to wait for the kernel to go and get the memory back from the pagefile. Now if you have an old PC and Windows Update is writing stuff to disk, it'll need to move the platter to the appropriate location in the pagefile, read out the memory, restart the thread and then move the disk back to the position that windows update was writing to.

Unsurprisingly this is slow, but the best solution really is to kill as many programs as you can, open Windows Update in the foreground and give it control of your machine for an hour and go and have lunch. Because you won't be doing anything with background processes, they won't complain so much that their memory is being swapped out, and the foreground thread gets a priority boost to CPU and have pages swapped out less frequently so Windows can spend more time running the programs on your machine and less time telling them to wait whilst it jumps the disk between the pagefile and the huge file you're trying to write.

@evildictaitor:

I don't think that's the cause, at least to my PC. I have 60% free memory out of 6GB. And my HDD is only two years old. This happens before login as well. Sometimes i leave my win7 running at login screen and playing xbox360, and i can hear mad clicking from my PC because of the automatic download.

@evildictaitor:

I don't think that's the cause, at least to my PC. I have 60% free memory out of 6GB. And my HDD is only two years old. This happens before login as well. Sometimes i leave my win7 running at login screen and playing xbox360, and i can hear mad clicking from my PC because of the automatic download.

4 hours ago, magicalclick wrote

@evildictaitor:

I don't think that's the cause, at least to my PC. I have 60% free memory out of 6GB. And my HDD is only two years old. This happens before login as well. Sometimes i leave my win7 running at login screen and playing xbox360, and i can hear mad clicking from my PC because of the automatic download.

Hard drive activity when the machine is idle might not be updates downloading. If your computer is idle long enough, Windows will start maintenance such as defrag.

@kettch:

I am very sure it is not defrag. I am sure I can reproduce it by simply doing a pure Image Recovery with no fragmentation.

So, no one experienced this? Strange.....

Windows Update (and especially Microsoft Update) has been a bloated pig for years on XP. It regularly takes 20 min and a couple hundred MB of RAM churning every month here on our dinosaur machines (P4 2.4GHz with 512-1024MB RAM). I've always assumed it's grinding through some cache of files detailing every patch installed to determine which new ones to download, But whatever it is, it is not efficient about doing it.

I've never noticed an issue on my Vista or Win 7 machines at home though.

14 hours ago, DCMonkey wrote

I've never noticed an issue on my Vista or Win 7 machines at home though.

XP has to go off and check lots of different system files to identify what versions are present, which I suspect (combined with the large amounts of downloading small files) is probably responsible for all the hard drive activity.

The servicing stack was completely redesigned for Vista to use the WinSxS folder full of hardlinks. This massively reduced the amount of work needed to identify what versions of files are on the system (it's effectively just a directory check) which makes servicing a lot faster and more efficient.

I think I may have finally figured out why WU pigs out like this on older machines. I don't know why I didn't think of it earlier but I ran Procmon on wuauclt.exe while it was checking for updates to see what it was churning through and it was mostly reads from c:\windows\SoftwareDistribution\DataStore\Datastore.edb 

I googled that and found some discussions about deleting datastore.edb and the associated log files and so far it seems to have made things better. Mine was about 170MB. After deleting it and restarting WU, it rebuilt the file to about 6MB. I'm guessing it was loading/indexing the whole thing into RAM, causing swapping and other performance issues.

Supposedly the only thing you lose is the update history. I can live with that to avoid my older systems becoming unusable the second Tues of every month.

Jan 12, 2012 at 3:07 AM, DCMonkey wrote

Windows Update (and especially Microsoft Update) has been a bloated pig for years on XP.

I've never noticed an issue on my Vista or Win 7 machines at home though.

Windows Update was completely rewritten between XP and Vista.