HP Capacity Advisor 7.2 User Guide

Table 31 Units and Terminology (continued)
Measured in MB/s (10^6 bytes, megabytes per second).
Each sample represents an average reading over the past five minutes. These measurements
are obtained and calculated in the following manner:
Table 33 Data collection for disk I/O bandwidth utilization by platform
Collected fromCalculationPlatform
pstat()Total bytes transferred during the intervalHP-UX
/proc/diskstatsTotal bytes transferred during the intervalLinux
WMI counterTotal bytes transferred out during the intervalMicrosoft Windows
HP Virtual Machine
Management Pack
(VMM)
Imported as isProliant VM Host and
VMs
sys$getdvi system
service DVI$_OPCNT)
Total bytes transferred during the intervalOpenVMS
disk I/O bandwidth
utilization
Gigabytes. Unit used for memory: (10^9 bytes)GBs
Gigahertz. In Capacity Advisor, CPU capacity is defined in terms of clock speed expressed in
megahertz (10^6 hertz) or gigahertz (10^9 hertz). Clock speed refers to the rate at which a
computer performs its most basic operations such as adding two numbers.
GHz
The difference between the average resource utilization on a system and the maximum available
capacity. See “Headroom” (page 25) for an explanation of headroom rating (stars), and
information on interpreting the star ratings shown in automated solutions.
headroom
Capability of some Intel processors to create an additional virtual core that provides additional
processing efficiencies. Note that Capacity Advisor does not count Hyper-Thread virtual cores
separately.
Hyper-Threading
In Capacity Advisor, the hypervisor includes not only the virtualization platform, but also all
functions performed by the host OS, as well as all virtual machine monitoring processes
(everything on the VM host that is not a VM guest).
hypervisor
Capacity Advisor estimates hypervisor memory overhead by adding together all memory used
in support of running guests. This overhead can be estimated by adding together the memory
use of the following:
• The host operating system on which the hypervisor is running (HP-UX, Linux, Windows).
• The hypervisor process that manages and enables the execution of guests.
• An overhead constant per guest that can either be a standard value for each guest on the
host, or a function of the amount of RAM allocated to a guest depending on the virtualization
platform.
Except in the case of HP Virtual Machine, Capacity Advisor assumes a worst case scenario
where all guests are allocated 1 GB of memory, as this will maximize the hypervisor memory
overhead.
hypervisor memory
overhead
Megabits (10^6 bits) per second. Unit used for networking throughput.Mb/s
Megabytes per second (10^6 bytes per second). Unit used for storage media throughput.MB/s
212 Units and terminology