Specifications

Table Of Contents
VMware Server Administration Guide
156 VMware, Inc.
the!host!operating!system!cannot!use!this!memory!itself!or!allow!other!applications!to!
use!it.
Virtual Machine Overhead
Virtual!machines!require!relatively!large!amounts!of!memory!to!operate!with!
reasonable!performance.!An!individual!virtual!machine!can!use!at!most!the!amount!of!
memory!specified!in!its!configuration!file!plus!some!overhead.!The!amount!of!
overhead!memory!required!depends!upon!the!size!of!the!guest’s!virtual!disks,!its!
behavior,!and
!the!amount!of!memory!allocated!to!the!virtual!machine.!Refer!to!the!table!
below!for!the!typical!upper!limit!needed,!based!on!the!amount!of!memory!allocated!to!
the!guest.
The!amount!of!RAM!actually!used!for!a!particular!virtual!machine!varies!as!a!virtual!
machine!runs.!If!multiple!virtual!machines
!run!simultaneously,!they!work!together!to!
manage!the!memory.
The!recommended!amount!of!RAM!to!specify! for!all!running!virtual!machines!is!
calculated!on!the!basis!of!the!host!computer’s!physical!memory!and!is!displayed!in!the!
memory!settings!slider!control!!Host!>!Settings!>!Memory.!If!you!want!
VMware!
Server!to!use!more!or!less!physical!memory,!use!this!slider!to!change!the!amount.
If!you!set!this!value!too!high,!the!host!may!thrash!when!other!applications!are!run!on!
the!host.!If!you!set!this!value!too!low,!virtual!machines!may!perform!poorly!and!you!
cannot!run!
as!many!virtual!machines!at!once.
Using Additional Memory
By!default,!VMware!Server!limits!the!number!of!virtual!machines!that!can!run!at!once!
based!on!the!amount!of!memory!specified!in!the!Host!Settings!dialog!box.!This!limit!
prevents!virtual!machines!from!causing!each!other!to!perform!poorly.!If!you!try!to!
power!on!a!virtual!machine!and!there
!is!not!enough!memory!available,!a!warning!
appears!and!the!virtual!machine!fails!to!power!on.
To!increase!the!number!or!memory!size!of!virtual!machines!that!can!run,!adjust!the!
amount!of!virtual!machine!memory!that!the!host!operating!system!may!swap!to!disk.!
Table 6-1.
Amount of Memory Allocated to the
Virtual Machine
Additional Amount of
Overhead Needed
Up!to!512MB Up!to!54MB
Up!to!1000MB Up!to!62MB
Up!to!2000MB Up!to!79MB
Up!to!3600MB Up!to!105MB