Simpler Navigation for Servers and Operating Systems - Please Update Your Bookmarks
Completed: a much simpler Servers and Operating Systems section of the Community. We combined many of the older boards, so you won't have to click through so many levels to get at the information you need. Check the consolidated boards here as many sub-forums are now single boards.
If you have bookmarked forums or discussion boards in Servers and Operating Systems, we suggest you check and update them as needed.
Operating System - Microsoft
cancel
Showing results for 
Search instead for 
Did you mean: 

Need help with configuring page file size and config

SOLVED
Go to solution
Sandy Wood
Frequent Advisor

Need help with configuring page file size and config

We've got a file server that's getting some high memory pages/sec readings and we're trying to make sure our paging file size and placement are optimal.

We've got 6 Raid5 logical drives and a system partition on C:, not raided. We have 3gb or ram in the machine. Perfmon shows a very steady Available bytes of about 2.5 GB of ram at all times. It doesn't drop even when the pages/sec spikes.

I've read that one should not place a paging file on mirrored or raid drives so I'm in a quandry on how to configure and locate the page file(s). Should we spread it out amongst the raid drives or leave it on just one?

Our paging file size is currently 4.3GB spread out over 3 drives.
8 REPLIES
Guy Humphreys
Valued Contributor
Solution

Re: Need help with configuring page file size and config

Sandy,

This is quite a tricky area and is open to debate. You are right when you say it is a bad idea to put a pagefile on a RAID 1 set, RAID 1 is very good for reading data but bad when writing and a pagefile needs to do both.

Please note in all the below discussions, I am referring to hardware RAID levels, as you are no doubt aware software RAID is a very poor relative compared with H/W.

I usually just put my pagefiles on a RAID 5 array - this works and works well enough. However this is not the best way if performance is your goal. A very good solution would be to have the pagefile location on a single disk on it's own disk controller, this as you can imagine is hard to justify from a cost point of view and it is also bad from a redundancy viewpoint, if the drive fails your pagefile is gone and more than likely the server will crash. (hard to say exactly as the server may not have been using the pagefile at the time of the crash so you could be OK, but can you take the chance?)

So, to gain some redundancy it would seem logical to use a RAID1 array, but this gives us the problem of poor write speeds once more, so we have to move to the next level of RAID - 0+1, this provides fault tolerance and performance but at a greatly elevated cost. You need to purchase 4 disks just to sit your pagefile on, and again if you want ultimate performance you don't want anything else accessing this array so it is also inefficient from a disk space point of view.

As far as the size of the page file goes, I always set mine to 2x RAM, initial and max size set to the same value to make sure I have a contiguous pagefile - better performance than letting windows allocate the size dynamically.

There are some more details from MS here:
http://www.microsoft.com/technet/archive/winntas/maintain/optimize/instant.mspx

HTH
GUY
'If it ain't broke, don't fix it!'
Jon Finley
Honored Contributor

Re: Need help with configuring page file size and config

I think that guy has about answered your question, and I agree that there shouild be NO problems with your Paging file on RAID 5, the only differences we may have is in the SIZE of the Paging file.

The desired size will vary depending on WHAT Applications are installed, and the general USE.

start with 1.5 X installed memory for a "general" server.

An Oracle server may require 3 X installed memory.

If your server is somewhere inbetween, increase it up from 1.5 to sowewhere below 3 X memory.

I DO strongly agree that the min and max sizes should be the same value. This has done 2 things for my servers: No fragmentation of the paging file. Faster startup time.

Jon
"Do or do not. There is no try!" - Yoda
Jon Finley
Honored Contributor

Re: Need help with configuring page file size and config

Sorry Guy... Somehow the Caps didn't take when I typed your name in. :-)

Jon
"Do or do not. There is no try!" - Yoda
Guy Humphreys
Valued Contributor

Re: Need help with configuring page file size and config

That's alright John, they somehow made it when I typed it out initially!

cheers
Guy
'If it ain't broke, don't fix it!'
Guy Humphreys
Valued Contributor

Re: Need help with configuring page file size and config

Sorry - Jon - my fingers are not having a good time today!
'If it ain't broke, don't fix it!'
Guy Humphreys
Valued Contributor

Re: Need help with configuring page file size and config

Sandy,

Jon is correct with his sizing rules, I use 2x RAM as that is what I have always used but it is purely a rough guideline, I find it to work in 95% of my servers. 1.5X to 3X is what is considered to be the norm in page file size.

You should set it to what the application vendor recommends and/or do some perfmon profiling to make sure it is running optimally.

Cheers
Guy
'If it ain't broke, don't fix it!'
Sandy Wood
Frequent Advisor

Re: Need help with configuring page file size and config

Thanks, guys, for all the input. This helps to clear up many of the issues I've been poring over.

One other issue I'm working with is the fact that I have 5 Raid5 logical drives on one file server, that just serves files only, this system doesn't have any other roles. I've had people tell me I should put the page file on one of those Raid5 drives and then others say I should split the pagefile up between the entire 5 drives.

Has anyone wrestled with this one?
Guy Humphreys
Valued Contributor

Re: Need help with configuring page file size and config

no problem Sandy, if you have found any solutions helpful you can assign points to the relevant person:

http://forums1.itrc.hp.com/service/forums/helptips.do?#34

w.r.t. file server page file, I would put it on one logical volume. RAID 5 is more than adequate for a pure file server. I can't think of any reason for it to span logical drives, unless of course you run out of space on one of the drives. I am assuming you are using a HP/Compaq server and that the raid volumes are already setup in hardware.

As an aside you don't HAVE to put it on C: drive you can put it where ever you have space. The only reason to put it on C : is so you can save memory dumps in the event of a blue screen. These are really only of use if MS or HP ask for them, the Blue screen code itself should be stored in the event log and you can always add in some more swap space after a crash so that if HP or MS request it you can get it next time it crashes. Although of course if you have space on C: you may as well use it.

HTH
Guy
'If it ain't broke, don't fix it!'