Page / Swap File Settings, what do they mean? 1

[1DMF]

Hi,

Ok I know what a swap file is, and how it is used as additional memory / memory dumping ground for aged memory data.

I've notice, (don't go to this setting very often), that there were multiple swap files set, one for each partitioned drive.

How is this used, does that mean when ever the D: drive is accessed and swaping is required it used the D: drive swap file and thus if C: then it uses the C: swap file.

Or is this like spanning the swap file across multiple drives, so if I have a swap file on C: of 4GB and of 4GB on D: , then the total swap file is 8GB?

Or is it something completely different.

I've had to remove the current C: drive swapfile do to @400MB free space!!!!!

Just wondered what the effect is, I've set the D: swapfile to 'system managed' and appreciate insight into the workings of the swap file setting on multiple drives in Windows 2003 Server SBS Premium.

Many thanks,

1DMF


"In complete darkness we are all the same, only our knowledge and wisdom separates us, don't let your eyes deceive you."

"If a shortcut was meant to be easy, it wouldn't be a shortcut, it would be the way!

 

[xmsre]

No pagefile on C: means you can't do a dump if things go south. Your server may need an enema or something...

http://support.microsoft.com/kb/555223/en-us

http://support.microsoft.com/kb/237740/en-us

http://support.microsoft.com/kb/889654/en-us

http://support.microsoft.com/kb/254649/en-us

 

[1DMF]

Thanks for the info.

A bit hard going first read for some of it, but the jist I get is this...

Multiple swap files = greater virual memory, it uses all swap files as required.

Swap size = generally shuld be @ 1.5 actual memory , though it's not set in stone, I always had the impression it was 2x actual memory, there is a however...

Only with Win2003 SP1 or > can you create an individual swap more than 4GB unless you force PAE usage via boot.ini.

Also if you have 4GB installed , you need to make swap file minimum 1MB more than 4GB on the system drive to get a memory dump, plus again boot.ini needs to be edited to add the MAXMEM switch.

What i didn't realise is the swap file / virtal memory is used sometimes instead of real memory and can have cases on some servers of using up virtual memory before real memory ? seems bizzare as you'd want real memory used when ever possible due to speeds compared to accessing disk drive.

But the long and the short is we have a system drive issue, as there is not enough space to give the C: swap file 4GB + 1MB.

Is this also an indication that you can span the pagefile across drives or even folders on same drive, but it will want to use a swap file on the system drive above any other, even though I have a swap file on the D:drive.

What's the implications of not being able to do a memory dump?

Is having no system swap file also detrimental to server performance?



"In complete darkness we are all the same, only our knowledge and wisdom separates us, don't let your eyes deceive you."

"If a shortcut was meant to be easy, it wouldn't be a shortcut, it would be the way!

 

[xmsre]

Buggy kernal mode drivers happen all the time. If you can't take a dump, you'll never be able to sort it out and find root cause.

When you span the page file across multiple disk, you're spanning: C: fills first, the next drive, then the next ...

Different process have different needs at different points in time hence minworking set and maxworking set. You can lock pages in RAM, at the expense of the performance of other process, and it's something you normally wouldn't do because of that impact. When a process is cruising along at the minimum workingset size and sudeenly needs some more memory, something has to give; least used pages from other processes are trimmed and paged out to disk. It a very dynamic interplay processes and their memory needs.

 

[1DMF]

If spanning is C: then D: , does that mean D: swap file isn't being used because it isn't an extention of a C: swapfile?

"In complete darkness we are all the same, only our knowledge and wisdom separates us, don't let your eyes deceive you."

"If a shortcut was meant to be easy, it wouldn't be a shortcut, it would be the way!

 

[xmsre]

No, the OS will use them in that manner even though it is not a single spanned file.

 

[1DMF]

Well at least we got 'A' swap file - lol.

Doesn't look like i'm getting any new IT equipment, so the C: drive will just have to lump it.

I could create a 2GB swap file now i've moved some programs and data, but that still doesn't solve the memory dump issue as it needs to be 1mb over 4gb!

Would you say it's still worth doing?

"In complete darkness we are all the same, only our knowledge and wisdom separates us, don't let your eyes deceive you."

"If a shortcut was meant to be easy, it wouldn't be a shortcut, it would be the way!

 

[xmsre]

If you can't make it large enough to do a full dump, at least make it large enough to do a kernal memory dump.

 

[1DMF]

and how big would that be? I'm assumiung 2GB is enough

"In complete darkness we are all the same, only our knowledge and wisdom separates us, don't let your eyes deceive you."

"If a shortcut was meant to be easy, it wouldn't be a shortcut, it would be the way!

 

[xmsre]

2GB plus 10MB.

John

 

[1DMF]

cool ,thanks for your help much appreciated.

"In complete darkness we are all the same, only our knowledge and wisdom separates us, don't let your eyes deceive you."

"If a shortcut was meant to be easy, it wouldn't be a shortcut, it would be the way!