page file in RAM only

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jmatwyko
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Joined: Thu Jan 28, 2010 12:37 am

page file in RAM only

Post by jmatwyko » Thu Jan 28, 2010 1:41 am

I'm currently running VSuite Ramdisk Standard Edition V4.4.4226.1353 on Windows 2003 Standard server. I've recently added 4GB more of ram to the server. The server now has 6Gb installed and the OS is using 4GB with PAE enabled. I have set up ramdisk drive using the 2GB (with reserved 128MB for video etc) of hidden ram on drive R: for pagefile. I've also set windows to only use the pagefile in Ramdisk. Performance is excellent with the pagefile in ram.

My question is should I create a hard disk page file just in case the pagefile in ram (R:) gets maxed out? And if I do create one will 2003 server use the one in RAM first as it is much faster? (the ramdisk drive should be used??? first as it is only used for pagefile.sys and has no other disk I/O)

Attached is a pic of the task manager, you can see that the limit commit charge is ~6GB. Before adding 4GB of new ram to the system the total commit charge would sometimes reach 4GB (and physical ram would be at 2GB). This brings the total to near 6GB which is what I have now of actual RAM. I used to have 2 pagefiles a small one on C: drive and a system managed one on a separate pagefile only hard drive.
taskman.JPG
taskman.JPG (46.41 KiB) Viewed 12366 times

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support
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Re: page file in RAM only

Post by support » Thu Jan 28, 2010 3:00 am

Hi,

From Microsoft,
http://support.microsoft.com/kb/314482/

It says,
The paging file on the less frequently accessed partition is used most frequently because it is on a partition that is least busy.
So if you set up a backup pagefile on system partition (eg. C:), this pagefile is used less frequently than the pagefile on a separate ramdisk dedicated to pagefile.

I saw the Peak Commit Charge is about 4GB and the Limit is about ~6GB from the figure you attached.
(Peak: the highest amount that the total commit charge has reached since the computer was last rebooted,
Total: current commit charge
Limit: physical memory available for paging + pagefile size)
So It's up to you whether to add a backup pagefile or not. If the Total completely reaches the Limit, a popup window will be displayed saying that "The system is out of virtual memory".

Hope this helps.
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jmatwyko
Posts: 3
Joined: Thu Jan 28, 2010 12:37 am

Re: page file in RAM only

Post by jmatwyko » Thu Jan 28, 2010 3:31 am

Thanks for the reply. I was trying to get away from adding more disk I/O to the C: drive. I suppose I could pull the global spare out of the raid 10 array and set a small swap file on it. It would see no other use just pagefile, then setup performance counters and see how much usage it gets compared to the pagefile in Ramdisk R: drive.

I post back later next week with some real world results.

cheers,
jeff

jer1956
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Joined: Tue Jan 19, 2010 4:29 pm

Re: page file in RAM only

Post by jer1956 » Sun Jan 31, 2010 3:38 pm

You might try adapting this method:-

http://support.microsoft.com/kb/237740

The use of seperate folder for each page file makes it easier to track how big each pagefile is. Setup the ramdisk to create a custom folder called pagefile1. Create another folder on the hard drive called pagefile2. Use regedit as described in the linked article. Providing the min value for the second pagefile is 0 it should not get used until the first is full. The operating system may ignore the second pagefile if it's on a differerent drive. This mechanism was not designed for this purpose but it might work!

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support
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Re: page file in RAM only

Post by support » Mon Feb 01, 2010 3:37 am

Recently I do an test on a WN XP sp3 platform, but the result is somewhat disappointing and confusing.
I set up 3 pagefiles on different partitions as below
C: (boot partition, physical hardisk) 50-100MB (min-max)
D: (C, D are both on the same physical harddisk) 50-100MB
Z: (ramdisk) 50-100MB

And then I use Performance counter to moniter all three paging files.
(Control Panel->Administrative Tools->Performance->Add Performance object: Paging File, and select "All instance")
The result shows that all 3 paging files are used with the certain ratio of usage. When system runs out of the initial paging amount (total 150 MB), the first growth occurrs on C:\pagefile.sys! This seems really strange.

So I think the safest method to set up two paging files is below:
ramdisk: Initial value: as much as you want.
other partition: Initial value: 20MB (can't be too small, otherwise will failed to create pagefile.sys on this partition)

hi jer1956, I also tried the method you wrote, however it might not work that set min value for the second pagefile to 0. The second pagefile doesn't be created when system runs out of the first pagefile (max value).
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jer1956
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Re: page file in RAM only

Post by jer1956 » Mon Feb 01, 2010 1:50 pm

Perhaps the solution is to create a fixed size pagefile on the ramdisk. Then "growth" of other pagefiles will only be required when that's full, which is what the OP wants' anyway! I have now setup my hard disk pagefile to be variable between 25 and 4000 so that it get's created on boot. I have also noticed that if you set them using regedit and then modify then using the normal System Tab the order reverts back to hard disk first in the registry.

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support
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Re: page file in RAM only

Post by support » Tue Feb 02, 2010 12:34 am

I agree with you.

pagefile on Ramdisk: fixed size
The secondary pagefile.sys: initial value: 20MB or more (just let the system can create the pagefile on bootup. Windows says that minimum value allows to be 2MB, it seems not correct.)

PS. It is reasonable that the normal System Tab will change the order becuase it also writes that registry value according to its harddisk order.
jer1956 wrote:I have also noticed that if you set them using regedit and then modify then using the normal System Tab the order reverts back to hard disk first in the registry.
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jmatwyko
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Joined: Thu Jan 28, 2010 12:37 am

Re: page file in RAM only

Post by jmatwyko » Tue Feb 02, 2010 7:11 am

You could set the registry permission so that SYSTEM has read only access to those keys. That should prevent those changes from occuring.

jeff

jer1956
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Re: page file in RAM only

Post by jer1956 » Thu Feb 04, 2010 10:34 am

Well I tried using XP monitor as desrcibed by "Support" and even with a fixed size pagefile on the ramdisk the hard disk page file was still used! The OP could try my setup and have a ramdisk using IM memory and Dynamic Memory. Providing the initial size of the page file is smaller than the IM memory no "normal" memory will be used until the page file needs it and the ramdisk expands into normal memory to accomodate it.

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support
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Re: page file in RAM only

Post by support » Thu Feb 04, 2010 11:48 am

yes, that's why I say it is better to set the initial value of secondary paging file to about 20MB if two paging files are set up. Thus the system uses only ~20MB of the secondary paging file before system uses up the paging file on the ramdisk.

For eg.
ramdisk pagingfile: 1000MB ~ 1000MB
harddisk pagingfile: 20MB~1000MB

The system will try to use up all the initial paging files and at most 20MB of the harddisk paging file is used before expand the amount. This will make the system fully utilize the pagingfile on the ramdisk.

Now let's change the settings on ramdisk, saying
ramdisk pagingfile: 500MB ~ 1000MB
harddisk pagingfile: 20MB~1000MB

In this case, the system may increase the harddisk paging file at first if the intial 520MB is used up.

next post we will see how windows determine which paging file is increased at first
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