Purging Prefetch - How quickly does XP recover ?

CCleaner for Windows
1

To update a software package I may need to first remove the prefetch files that were used by the previous version.

I think rather than identifying and then removing all related prefetch files it would be much faster and easier to simply delete everything in prefetch.

It now takes about 30 seconds from leaving BIOS to get the login screen,

and another 30 seconds from login before it is ready for me to launch whatever I choose,

and if I am still getting coffee when it is ready for me, the HDD still has busy bursts for another 30 seconds as it remembers a few more things it needs to do.

When I launch Firefox that takes about 10 seconds.

I believe deleting prefetch does no harm other than being a little slower, and it will automatically rebuild prefetch and then get up to speed.

I would appreciate advice upon how much longer it would take to start up after a purge,

and how many reboots for it to rebuild prefetch and get back to speed,

and how many times would I need to launch Firefox before that also was up to speed.

Are there any other issues I should be aware of ?

Background to my interest :-

Some software can be auto updated "in-place".

Some requires un-install of the old before the new will load.

Some may fail to update for many reasons :-

1) the MSI installer trips and stumbles over old remnants that were not removed ;

2) Windows Security Centre blocks an A.V. / Firewall update until the repository is rebuilt ;

3) Other Windows gotcha's too numerous to mention.

Comodo security is this sort of software.

An upgrade will, with luck, only require the use of Windows Add/Remove to purge the old before installing the new,

but when luck runs out there is a script to purge traces of the old from the registry and files/folders.

I have now encountered a view that even the old prefetch files should be removed,

and it seems to me much easier and more reliable to purge all prefetch instead of individual identification and deletion.

Regards

Alan

2

Watch the *.pf files (sort them on date) and you'll see that a *.pf file is updated every time when you open the corresponding application (e.g. Firefox).

3

I have read to not delete "Layout.ini" nor "NTOSBOOT-********.pf". One thing causes doubt, though: my Layout.ini file has references to some really old obsolete apps which are now gone. So I don't understand all about it.

This site says not to delete Layout.ini, but then says at the bottom that 3 reboots will rebuild Layout.ini if you mess it up. SITE

My personal experience is that on occasion I have deleted just about all of them except the 2 mentioned and could not see that it made much time difference, at least after a couple of reboots.

4

I have read to not delete "Layout.ini" nor "NTOSBOOT-********.pf". One thing causes doubt, though: my Layout.ini file has references to some really old obsolete apps which are now gone. So I don't understand all about it.

This site says not to delete Layout.ini, but then says at the bottom that 3 reboots will rebuild Layout.ini if you mess it up. SITE

My personal experience is that on occasion I have deleted just about all of them except the 2 mentioned and could not see that it made much time difference, at least after a couple of reboots.

You can safely delete all contents inside prefetch folder. The NTOSBOOT.pf is for system loading. You just will notice your system loading at a slower pace. They will always be recreated after a while. I currently have all prefetch disabled save NTOSBOOT.pf and Layout.ini

5

The Prefetch folder should never be deleted. Please read this : http://www.edbott.com/weblog/2005/06/one-more-time-do-not-clean-out-your-prefetch-folder/ :)

6

The Prefetch folder should never be deleted. Please read this : http://www.edbott.com/weblog/2005/06/one-more-time-do-not-clean-out-your-prefetch-folder/ :)

That does seem to be the majority opinion. Both links say don't do it, and also say that the prefetch file is self maintaining. I believe both assertions to be true.

I should clarify my earlier statement. At one time or another, I have deleted most of the individual prefetch files, ending in .pf, sometimes many of them at once, with little noticeable effect. Wouldn't suggest anyone else do that, since the tech community seems to be against it.

Alan_B, I suspect you already knew most of this...but...your inquiry was not about whether to do it, but how long it takes to get back to normal. If any of these links are to be believed, the answer is either 3 reboots or 72 hours. :P

7

Thanks one and all.

Before posting I did Google and came across Edbott's strong views against deleting Prefetch.

There seemed to be never-ending controversy in the comments section, never-ending till the topic got locked ! !

I think I will bow to the majority view that you share.

I am not convinced that deleting everything other than layout* and BOOT* pf will do me harm,

but I realise that if I propose this as a good way to ensure removal of all remnants I will have far too many negative comments to respond to ! !

Regards

Alan

8

The Prefetch folder should never be deleted. Please read this : http://www.edbott.com/weblog/2005/06/one-more-time-do-not-clean-out-your-prefetch-folder/ :)

I have read that article. Depending on how fast your PC is you may notice no improvements when Prefetch is active. For me, it seems prefetch doesn't give me that claimed performance boost. Maybe that's because I have NTFS compression ON. I also tend to pack executables with an exe packer.

I did a test using a cronograph: Paint Shop Pro X13 loaded a few seconds faster with prefetch off. Also, very small executables load faster, because with prefetch off there are less hard disk reads involved.

Your mileage may vary, as always. Just do some tests and use the setting that best suits your system.

9

I have read that article. Depending on how fast your PC is you may notice no improvements when Prefetch is active. For me, it seems prefetch doesn't give me that claimed performance boost. Maybe that's because I have NTFS compression ON. I also tend to pack executables with an exe packer.

I did a test using a cronograph: Paint Shop Pro X13 loaded a few seconds faster with prefetch off. Also, very small executables load faster, because with prefetch off there are less hard disk reads involved.

Your mileage may vary, as always. Just do some tests and use the setting that best suits your system.

Thanks. Good to see support for my idea that prefetch causes extra delay when only a small exe is loaded.

I never use NTFS compression because :-

It actually wasted disc space by creating an UNcompressed duplicate in dllcache for any important executable,

Windows File Protection does NOT trust NTFS protection and carefully evaluates every important exe that is compressed,

Windows File Protection DEMANDS my Windows installation disc (not available on pre-installed system) if the compressed exe fails evaluation, even though MD5 checksum is the same before and after.

It makes Acronis partition backup image LARGER not smaller, even when only "unimportant" documents are compressed, because NTFS compression is supposed to be LOSSLESS, i.e all the original information is retained, and there is an addition burden of information to facilitate subsequent DE-compression. Acronis achieves very little EXTRA compression on files already NTFS compressed, and for every compressed file it also has to include the decompression dictionary or whatever NTFS used for its compression.

I am quite certain that my experience with Acronis will be repeated with ANY backup system that uses compression to occupy less disc space than the sum total of original files - many times you win but sometimes you lose.

Regards

Alan

10

Well, if your system takes a long time to start up then remove a lot of start up options you never or rarely use.

11

Well, if your system takes a long time to start up then remove a lot of start up options you never or rarely use.

To expand on my first post, 30 seconds from power-on to log-on, then 22 seconds to load my profile plus 8 seconds to create my ERUNT registry backup. If it was any faster I would not get my instant coffee made in time ! !

Speed is not the problem.

I just wanted to know if Windows moved with the speed and grace of a glacier without the benefit of prefetch, and how long (no. of reboots or days) before it would be back to speed.

Right now Task manager shows only 23 processes running, which includes Taskmgr.exe, Firefox.exe and plugin-container, and two Comodo security processes.

When I prepare for shutdown it drops to only 20 processes, and on start-up only 1 or 2 others whilst Windows looks for updates and gets busy with a few tweaks.

I think for a 7 or 8 year old XP Laptop I now have a fairly lean system.

Regards

Alan

12

Alan_B:

OFFTOPIC

I see several improvements on space saving when using NTFS compression. This is specially true for me when playing games. Some of them get compressed almost 30-50%. It's a tradeoff between access speed and space savings. Another thing I noticed is that when dealing with compressing data you "save up" some space of disk cache in memory. I mean, I think disk cache memory space holds more data when reading from compressed files.

I haven't experienced the problems you are having when making backup copies. I use Drive Image XML. Backup size is almost identical for me.

BACK ON TOPIC...

I think Prefetch is not so hot, at least under Windows XP. Even with prefetcher disabled, loading applications is just slow the first time. Next subsequent loads are taken from disk cache. And, it's true, loading small executables takes more time when prefetcher on. I don't know if Superprefetch (present I think under Vista/7) is doing a better job or not.

13

Superfetch is completely different from the Prefetch - it loads commonly used files directly in memory, and releases them if that memory is needed by something else. ;)