1.Target Mode: The administrator specifies a memory target for the guest.XenServer adjusts the guest's memory allocation to meet the target. Specifying a target is particularly useful in virtual server environments, and in any situation where you know exactly how much memory you want a guest to use. XenServer will adjust the guest's memory allocation to meet the target you specify.

2.Dynamic Range Mode: The administrator specifies a dynamic memory range for the guest; XenServer chooses a target from within the range and adjusts the guest's memory allocation to meet the target. Specifying a dynamic range is particularly useful in virtual desktop environments, and in any situation where you want XenServer to repartition host memory dynamically in response to changing numbers of guests, or changing host memory pressure. XenServer chooses a target from within the range and adjusts the guest's memory allocation to meet the target.

Note:

It is possible to change between target mode and dynamic range mode at any time for any running guest. Simply specify a new target, or a new dynamic range, and XenServer takes care of the rest.

Memory constraints

XenServer allows administrators to use all memory control operations with any guest operating system. However, XenServer enforces the following memory property ordering constraint for all guests:

0 memory-static-min memory-dynamic-min memory-dynamic-max memory-static- max

XenServer allows administrators to change guest memory properties to any values that satisfy this constraint, subject to validation checks. However, in addition to the above constraint, Citrix supports only certain guest memory configurations for each supported operating system. See below for further details.

Supported operating systems

Citrix supports only certain guest memory configurations. The range of supported configurations depends on the guest operating system in use. XenServer does not prevent administrators from configuring guests to exceed the supported limit. However, customers are strongly advised to keep memory properties within the supported limits to avoid performance or stability problems.

Operating System

 

 

Supported Memory Limits

 

 

 

 

 

 

 

Family

Version

Architectures

Dynamic

Dynamic

Additional

 

 

 

Minimum

Maximum

Constraints

 

 

 

 

 

 

Microsoft Windows

XP (SP2, SP3)

x86

256 MB

4 GB

Dynamic Minimum

 

 

 

 

 

¼ Static

 

Server 2003

x86 x64

 

 

 

256 MB

32 GB

Maximum for

 

 

 

 

 

all supported

 

Server 2008

x86 x64

512 MB

32 GB

operating systems

 

 

 

 

 

 

 

Server 2008

x86 x64

512 MB

32 GB

 

 

R2

 

 

 

 

 

 

 

 

 

 

 

Vista

x86

1 GB

4 GB

 

 

 

 

 

 

 

 

7

x86

1 GB

4 GB

 

 

 

 

 

 

 

65

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Citrix Systems 5.6 manual Memory constraints, Supported operating systems