65
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
Minimum
Dynamic
Maximum
Additional
Constraints
XP (SP2, SP3) x86
≥ 256 MB ≤ 4 GB
Server 2003 x86 x64
≥ 256 MB ≤ 32 GB
Server 2008 x86 x64
≥ 512 MB ≤ 32 GB
Server 2008
R2
x86 x64
≥ 512 MB ≤ 32 GB
Vista x86
≥ 1 GB ≤ 4 GB
Microsoft Windows
7 x86
≥ 1 GB ≤ 4 GB
Dynamic Minimum
≥ ¼ Static
Maximum for
all supported
operating systems
