Dell Vizioncore Podręcznik Użytkownika Pobierz pdf (Strona 11)

vReplicator v2.5 Chapter 2 Installation 8

between hosts. Even after a vMotion event occurs, replication activities can continue

unabated.

VSS

The Microsoft® Volume Shadow Copy Service (MS VSS) driver in vReplicator works in

conjunction with Vizioncore’s VSS agent to ensure reliable remote API call

communication. By alternately freezing and thawing application writes, MS VSS and

Vizioncore VSS provide consistent results during each replication process. VSS enables

quiescing—or pausing—of application writes when database servers such as SQL and

Oracle are being replicated.

vzBoost

In vReplicator, vzBoost is an optional driver that improves write speeds to the Virtual

Machine File System (VMFS). vzBoost manages Service Console traffic; it has no

input/output (I/O) impact on running VMs. The driver is enabled through

Tools→Preferences→ESX Server and is installed on the destination ESX host.

vReplicator activates the driver when a write to VMFS is initialized. The driver remains

activated only for the duration of the write. As soon as the data transfer completes, the

driver becomes inactive and no longer taxes system resources.

Differential Replication

In differential replication, the source Virtual Machine Disk Format (VMDK) is scanned.

A data map is created during the first replication pass. When the first snapshot is taken,

disk writes are suspended temporarily. The snapshot remains open. An empty virtual

disk—called the delta file—is added. As data is replicated, this file grows. These changes

are merged back into the VMDK and the snapshot is closed. During the second

replication pass, a snapshot is opened. On the vReplicator box, the source VM’s current

data is compared to the changed data stored in the data map. These changes are

replicated, block by block, and committed to the destination machine. Then, the snapshot

is closed and the VMDK is opened. The entire source VM image is replicated to the

destination machine.

Hybrid Replication

Using the hybrid approach, replication is done as a function of change over time rather

than change to data. Snapshots can be taken at shorter intervals with no loss of data.

There is no need to scan during each replication pass. The differentials engine

resynchronizes the source and destination VMs selectively. Therefore, there is no need to

replicate the entire source image again, just to capture the data that changed between

snapshots.

During hybrid replication, two snapshots are created. One snapshot remains open

continuously. While the second snapshot is usually not visible to the user, it plays an

important role in replication. As time passes, the second snapshot fills with data.

1 2 ... 6 7 8 9 10 11 12 13 14 15 16 ... 188 189

Brak uwag

Dell Vizioncore Podręcznik Użytkownika Strona 11