Data Mirroring - Replicating data over a LAN or WAN
For a seamless recovery of your servers, SteelEye Life Keeper from Open Minds guarantees to provide you with a complete disaster recovery solution ensuring that you maintain business continuity. Our high availability solutions will grant continuous data protection providing data replication as well as the monitoring of all your servers to ensure failover through the Java GUI.
The ability to access meaningful data in a timely, efficient manner is
essential where access to customer information is critical. Of equal importance
is the ability to move and share data throughout the organisation - among
departments, offices, and business partners. The time it takes to recover from
a failure has to be shorter than ever to avoid the very serious consequences of
impacted productivity and profitability, damaged current and future revenues,
and lost confidence of customers.
One way of protecting data is to duplicate it in real time to another
system - using Data Replication or mirroring software. In the event of
one system failing, the standby system can come online (
automatically if LifeKeeper server manager is used) to
provide continuation of service, with minimal (if any) data loss
occurring.
Data replication can either occur locally over a LAN (removing the
requirement for expensive shared storage) or remotely over a WAN (so
forming part of a disaster recovery solution).
Data Replication is sold as an independent product or with LifeKeeper and can be used in one of three ways:
- To back up data real time to another server.
- With
LifeKeeper, to provide failover when no shared storage is available.
Use of data replication software can drastically reduce the cost of a
highly available solution by eliminating the need for shared storage.
- As an addition to LK cluster manager to provide an offsite copy of the data for disaster recovery.
Data replication features
Block level replication takes place over a TCP/IP link to a second
server. The servers can be connected via a LAN or WAN link. As the
replication is at block level, only changed data is replicated over to
the second server, avoiding the need for the additional traffic of file
level replication. LifeKeeper data replication contains the following features:
- The ability to rewind and recover to a point in time
- Bandwidth throttling
- The ability to set compression levels from 0-9
- WAN optimisation
LifeKeeper Data Replication integrates fully with LifeKeeper
clustering so it can be managed through the GUI together with any other
application software that is being protected. Use of data replication
eliminates the need for shared storage as data is always up-to-date on
the backup server.
Mirroring over LAN and WAN to multiple targets
It is possible to extend the mirror to replicate to more than one
target. The benefit of this is that a local and remote replica of
critical data can be produced which will further extend resilience.
A local replication (and failover) for use when there is a local
disruption to the active server, for example, if there is a failure of
the service or the server. A remote, off-site replication (and
failover) for site disasters.
Behaviour of the mirror
Mirroring is from source to target and can be paused by the administrator for a number of reasons:
- To perform a backup or other operations of the data that would
require the data but would affect the performance of the active system.
- To alleviate traffic in periods of peak usage of the network.
The mirrors can be re-activated at a convenient time and the data
will automatically resynchronize.
LifeKeeper keeps a bitmap of changed data on the mirror. If the mirror
is broken and resynchronization is required, then only the changed data
is resynchronized.
Connection
Replication takes place over a standard TCP/IP link, and so can
easily be tunnelled through a VPN to provide security and encryption
and can be used across a firewall simply by opening up the correct
ports. Because, after its initial synchronisation with the backup
server, LifeKeeper Data Replication only replicates the blocks that
have changed on the disk the bandwidth it requires is proportional to
the amount of data that changes on the source system, however if the
required bandwidth is unavailable for a period the mirror will pause
and can be restarted easily when the network quietens down.
Disk to disk backup
Data replication can be used as a stand-alone product to produce a real-time block level
backup of a volume or partition. The backup is to another server on a LAN or off-site over
a WAN.
Disk to disk backup is lower cost than a combining data replication and failover, but still
leaves the option of adding failover at a later date.
It can also be used as a means of consolidating backups of multiple servers onto one node.Other Uses
While disaster recovery is the most obvious use of disk to disk
backup, it can be used with off-host processing - movement of data to a
separate server from where it can be backed up to tape, have reports
run on it, be tested in a variety of ways, or any other task that
requires production data but that would effect the performance of the
production system.