Rob said earlier that after linux starts using a lower priority swap
area it doesn't "migrate back from swap2 to swap1 when stuff is freed
later."

So do you find after swapoff/on a high priority VDISK that linux starts
using it? or does it ignore it and keep filling the dasd swap?


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-----Original Message-----

From: The IBM z/VM Operating System [mailto:[EMAIL PROTECTED] On
Behalf Of Brian Nielsen
Sent: Monday, December 03, 2007 12:53 PM
To: [email protected]
Subject: Re: Is 275GB of VDISK stupid?

On Mon, 3 Dec 2007 08:43:45 -0500, Romanowski, John (OFT) 
<[EMAIL PROTECTED]> wrote:

>Now that the swap topic's open again:
>
>What is the basis for advising z/VM VDISK users to have a hierarchy of
>multiple linux swap areas of increasing sizes?   Are there feature(s)
of
>the swapping algorithm that make that hierarchy principle optimal?   

The configuration we use includes swap space on real DASD at a lower 
priority than the VDISK swap areas.  Over time Linux will swap more to
the 
real DASD than the VDISKs.  At this point doing a swap off and then on
of 
a VDISK swap area frees up the fast VDISK.  Having various VDISK sizes 
allows the flexibility of migrating smaller amounts of swap data during 
busy periods and larger amounts during slow periods.

Brian Nielsen

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