Specifications

Administration Guide
154 VMware, Inc.
Using Network-Based Replication Tools
You!can!configure!any!enterprise!disk!storage!subsystems!to!replicate,!or!mirror,!their!
data!to!another!subsystem!at!a!local!or!remote!location.!This!replication!can!occur!either!
synchronously!or!asynchronously,!as!described!below:
! If!the!replication!is!synchronous,!a!write!operation!does!not!appear!to!be!
completed!locally!until!the!data!is!committed!to!disk!at!the!remote!location.
Synchronous!replication!improves!data!integrity!but!presents!a!potential!
performance!bottleneck.
! If!the!replication!is!asynchronous,!the!remote!copy!is!permitted!to!be!some!number!
of!write!operations!behind!the!most!current!local!data.
Asynchronous!replication!accepts!a!higher!potential!of!inconsistent!data!at!the!
remote!site!in!exchange!for!increased!performance.!
You!can!use!either!of!these!hardware‐based!approaches!with!
ESX!Server.
In!addition,!some!disaster!protection!software!products!implement!remote!mirroring!
in!software.!These!tools!provide!protection!and!data!integrity!semantics!similar!to!those!
of!the!hardware‐based!solutions.!How ev er,!they!might!be!more!cost‐effective!for!
configurations!with!low!to!medium!performance!requirements.!
These!software!tools!can!be!used!
inside!guest!operating!systems.
N
OTE VMware!recommends!that!you!do!not!use!software!remote!mirroring!tools!for!service!
console‐driven!replication!on!VMware!ESX!Server.!This!is!because!these!software!tools!
usually!require!file!system!format!awareness,!add!significantly!to!the!network!I/O!level!
and!the!CPU!requirements!to!service!that!network!I/O,!and!are!more
!common!on!
Windows!and!UNIX!operating!systems!than!on!Linux.