Pagefile.sys

There are two types of inactive files in the pagefile, those that are left behind after a progam closes, which don't serve a purpose, and those that are linked to an active program, part of which is already in the RAM. When the program needs it, it is much faster to access the pagefile than go rumaging through the rest of the harddrive.

From what I have read, if a person is operating from a SSD, they don't need a pagefile. However, most of us don't have that luxury yet, and even if I did, I would still question deleting the pagefile, unless the SSD was big enough to contain all of the programs, as well as the OS, because I think that the contents of the pagefile consists primarily of program data, rather than that of the OS.

I also think that it depends a lot on the specific program in use, because I often find that the pagefile is not very active in my typical operations. Putting a small partititon for the pagefile has no impact on drive space, because it is so small. They say that the pagefile should be place on the fastest drive available, so this is negated if one has an SSD.

They also say that one should defrag the pagefile, but this is something that I have never got into, because the only way to do that would be to defrag at boot time. My defragger has that ability, but the last time that I tried that, it caused me a lot of trouble, because the program is set to use it's own video driver, rather than the one installed in Windows, and something went wrong, and I just got a black screen. I didn't learn until somewhat later that there is an option in the program configuration to cause it to use the system's driver instead of it's own. I can't understand why it doesn't use the Windows driver by default.

really its noy compulsory that you can set Pagefile.sys

pparks1 said:

BunBun said:

Until you go to access said inactive things... bam instant slow computer. No thanks.

What difference is there pulling the data from the page file which is on the hard drive or pulling it from the hard drive itself since it's not actively in RAM anymore. I don't see any reason whatsoever why it would be slower coming from the pagefile...it anything I would think it a bit faster than coming from the actual hard drive itself.

Hi there
without trying to get TOO technical you need to understand how an OS organises memory.

Very simply applications only need RAM when actual data instructions are being executed -- when an application isn't actually running (say in the other inactive windows) then parts of this application will be written to the Paging file. In addition depending on how you use the computer the OS will also store data it THINKS you'll need in future -- this is a complex algorithm but it actually works quite well and is known as "PRE FETCH" so when you need the data it's already in the system.

The paging file is also used when there isn't enough RAM in the system to run all the applications that the user wants to at the same time -- so again the "inactive" parts are copied to the paging file so RAM that is needed for another application is released and the data can be loaded to the freed "page". Of course if RAM is really short then the system will never run anything since it will be doing nothing but paging - this is called "thrashing" and you'll notice this by seeing a HDD light solid on and the computer won't be doing anything either.

Now this paging file is ALWAYS used by the OS - even if you "disable" a disk paging file and the default is usually 1/2 the main RAM size so if you have an 8GB system the OS will allocate a 4GB page file IN YOUR PRECIOUS RAM so your computer will effectively be a 4GB machine not an 8GB machine.

Now your system could hang in this case because once your paging file is full there isn't any area for the OS to write its temporary data to -- so your system will come to a total and 100% sudden HARD STOP.

So I would recommend NEVER disable the system paging file - and put it on THE FASTEST DISK(S) you have -- SSD's make a great place for paging files.

OS internals are complex -- but NEVER switch off the paging file even if you have oodles and oodles of RAM.

Finally Reading from the paging file IS different from reading normal data since this has the HIGHEST I/O priority and some of the data is always held in an internal "Instruction decode area" in the hardware chip. Paging info is often read whilst other operations are taking place so it's not a "normal data read" in the usual sense of the word.

Added

-- You NEVER need to defrag a pagefile -- it's re-built at each re-boot.

Also to the poster who is talking about "Virtual Memory" -- this is a DIFFERENT topic which involves swapping in and out users "Address spaces" and "data areas" in their entirety.
This can be a LONG slow process -- excessive "Swapping" will also kill a system stone dead - and is a sraight data address space image write.

Paging involves a totally DIFFERENT algorithm -- the two are often confused. Linux being a Multi User system will have provision for "Swapping" but Windows (not the SERVER versions) being a single user system won't need "Swapping" in the classical sense but will stick to paging.

Cheers
jimbo

And while it is taking the inactive portions of ram and putting it to the page file the system comes to the crawl as the HDD is flooding with excess IO's of data being written to the page file (that very well may never be needed again before next reboot) where as if you had enough memory in the first place its much faster to just leave everything there.

I always make sure I have enough RAM for my needed applications and when something crashes due to not having enough RAM I enable the pagefile temporarily and go buy more RAM.

And to your comment about only having 1/2 of your RAM availible that is completely false. I have run fire fox with over 100 tabs open, 2 wow's concurrently, along with vent, IM app, along with some other stuff useing ~90% of my 8GB of RAM without any slow downs or any issues. Do the same thing with pagefile active and my computer would slow down while the HDD is flooded with excess IO's from pageing. I have tested this extensively. Back when I had 2GB of ram I had games that would cause excessing pageing and slow my system.

With a Intel SSD this may not be the case but that is new technology and very expensive. Also I would want to disable the pagefile to save on the life of my drive and prevent all the blocks from being written to with a useless page file. I could see a pagefile bring a SSD to its lowest performance very quickly on a high memory usage machine. If I had to use a pagefile where my boot drive was a SSD I would buy WD Velociraptor as a dedicated pagefile drive.

EDIT:

Also your mention of pageing IO's given highpriority only make the writing to page file slower for everything thing else. And regardless of how it it accesses the data you are still restriced to the limitations of rotational HDD's which is multiple mangnitudes slower then RAM. (random read/writes are much less then 20mb/s on even the fastest drives while average RAM today operates between 5-10GB/s)

you won't actually use the pagefile unless your RAM overflows..
so there's no need to worry, even if you do have a pagefile..

and you can easily defrag it..
- just remove it (ie, set it to zero size) and then re-instate it again..
- this will clean it out completely, it isn't essential to defrag it anyway, as it's dynamic, ie it only expands when necessary..

- there used to be a gain in XP, if you set the pagefile to min and max at twice your system RAM and on a partition away from the OS
- this meant that the OS didn't need to keep a table indicating the pagefile's dynamic start position
- but you're only saving nano-seconds, and it's not really essential if you have a fast CPU and lots of RAM