Red Hat NETSCAPE MANAGEMENT SYSTEM 4.5 User Manual download pdf (Page 143)

Running VMware ESX Server

143

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You can combine these approaches with the ESX Server redo log API (described in

Providing Optimum Data Integrity In Virtual Machine Backups Without Downtime on

page 142) to keep the interval during which an extra log is used to a minimum. To do

this, take the following general steps:

• Add the new redo log.

• Take a snapshot of the mirror using your disk subsystem’s or volume manager’s

interfaces.

• Commit the changes to the live log.

You may still back up from the stable disk image on the snapped mirror, then

reconnect the mirror to have it pick up the latest changes in time for your next

backup.

Using Network-based Replication Tools

Many enterprise disk storage subsystems can be configured to replicate, or mirror,

their data to another subsystem at a local or remote location. This replication can

occur either synchronously or asynchronously.

• 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.

• This 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.

This accepts a higher potential of inconsistent data at the remote site in

exchange for increased performance.

Either of these hardware-based approaches may be used 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. However, they may be more cost-effective for

configurations with low to medium performance requirements.

These software tools can be used inside guest operating systems.

Note: We recommend that you do not use software remote mirroring tools for

console operating system-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.

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Red Hat NETSCAPE MANAGEMENT SYSTEM 4.5 User Manual Page 143