System information

Snapshot Software
Snapshot software allows an administrator to make an instantaneous copy of any single virtual disk defined
within the disk subsystem.
Snapshot software is available at different levels:
n
ESX/ESXi hosts allow you to create snapshots of virtual machines. This software is included in the basic
ESX/ESXi package.
n
Third-party backup software might allow for more comprehensive backup procedures and might contain
more sophisticated configuration options.
Administrators make snapshots for a variety of reasons:
n
Backup
n
Disaster recovery
n
Availability of multiple configurations, versions, or both
n
Forensics (looking at a snapshot to find the cause of problems while your system is running)
n
Data mining (looking at a copy of your data to reduce load on production systems)
Using a Third-Party Backup Package
Using third-party software has the advantage of a uniform environment. However, the additional cost of the
third-party snapshotting software can become higher as your SAN grows.
If you are using third-party backup software, make sure that the software is supported with ESX/ESXi hosts.
If you use snapshots to back up your data, consider the following points:
n
Some vendors support snapshots for both VMFS and RDMs. If both are supported, you can make either
a snapshot of the whole virtual machine file system for a host, or snapshots for the individual virtual
machines (one per disk).
n
Some vendors support snapshots only for a setup using RDM. If only RDM is supported, you can make
snapshots of individual virtual machines.
See your storage vendor’s documentation.
NOTE ESX/ESXi systems also include a Consolidated Backup component.
Layered Applications
SAN administrators customarily use specialized array-based software for backup, disaster recovery, data
mining, forensics, and configuration testing.
Storage providers typically supply two types of advanced services for their LUNs: snapshotting and
replication.
n
Snapshotting creates space with efficient copies of LUNs that share common blocks of data. In general,
snapshotting is used locally on the same storage systems as the primary LUN for quick backups,
application testing, forensics, or data mining.
n
Replication creates full copies of LUNs. Replicas are usually made to separate storage systems, possibly
separate sites to protect against major outages that incapacitate or destroy an entire array or site.
When you use an ESX/ESXi system in conjunction with a SAN, you must decide whether array-based or host-
based tools are more suitable for your particular situation.
Fibre Channel SAN Configuration Guide
72 VMware, Inc.