protection and quick recovery are critical requirements
for enterprises that have important business data growing
at a fast pace within their data centers or remote locations.
Here are some options for data protection and recovery
architectures in distributed and centralized storage
configurations. by Anal Jain
growth and investment on storage solutions within enterprises
is increasing at a fast pace. As businesses depend on
IT infrastructure for higher productivity and competitive
advantage, data protection and recovery become critical
for everyday business operations, especially during
major failures or natural disasters. This highlights
the need for data replication, backup, and restoration
of operations, based on optimal utilization of IT resources.
Today, customers are considering various approaches
for quick recovery to protect their valuable data and
mechanisms. Some of the factors which affect these infrastructure
and policy decisions are cost of downtime, backup windows,
time-to-recover, frequency of backups, and maturity
of technological options. Such decisions typically result
in a combination of online data replication (disk-to-disk)
or offline (disk-to-tape) backups and the implementation
of policies required with these operations.
Let's focus on data protection strategies and for networked
storage in both distributed and centralized topologies
based on Ethernet/IP network infrastructure.
Variety of features
Networked storage solutions should offer a variety of
features that address high availability and resilience
for data storage like clustered configurations, RAID
protection, and robust product architecture. The network
infrastructure supporting these storage topologies also
enhances the overall resilience of the solutions in
terms of high availability and security.
The key factor that drives the stringent requirements
for data availability is the cost associated with downtime.
This includes costs associated with lost productivity,
reduced customer satisfaction, and the opportunity cost
from lost revenues due to inability to access business-critical
Accidental data deletions and data corruption by an
application may lead to irrecoverable losses resulting
in significant effort and time expended to reconstruct
the data. To ensure data recovery from such catastrophes,
most IT organizations archive or backup to a relatively
inexpensive offline media, like tape. In most cases,
the periodic backup process is performed directly off
the production data, rendering it inaccessible to users
or applications during the backup cycle. This is due
to inherent limitations in the data transfer speed associated
with such media. Similarly, recovery of data from such
archives also leads to significant downtime.
Natural disasters like earthquakes, floods, and fire
can take the entire IT infrastructure down. In such
cases, reconstructing all the business-critical data
and rapidly recovering to full business operation can
be extremely difficult. Such data recovery could take
days, which could severely affect the functioning and
viability of an enterprise. Many far-sighted enterprises
implement disaster recovery plans to guard against this
A disaster recovery implementation typically involves
copying data from the production site to an online 'disaster
recovery' site. Such an implementation involves not
only infrastructure, but also people and process-related
A new breed of networked storage technologies called
Nearline, can provide a unique approach for LAN-based
backup. Nearline supports cost-effective disk shelves
with the purpose of providing faster disk-to-disk backup
mechanisms. Mirroring software can be used for asynchronous
data replication over an IP/Ethernet connection from
networked storage at remote sites to a Nearline appliance
located at the central site.
Online Data Protection Solutions
As the nature of data becomes more critical and the
cost of downtime increases, customers need to consider
solutions that allow data protection and recovery from
an online repository in addition to archiving to tape.
The cost of downtime in terms of its business impact
and customer satisfaction issues justifies these solutions
and topologies. The following section describes how
networked storage can be deployed to provide online
data protection, both within a data center as well as
in distributed environments.
In terms of online data protection, let's review the
relevant features that should be part of a networked
storage solution. The 'snapshot' feature enables users
to create instant online copies of data. Snapshots use
a copy-on-write technique to avoid duplicating disk
blocks that are the same in a snapshot as in the active
file system. Only when blocks in the active file system
are modified or removed do snapshots containing those
blocks begin to consume disk space. There is no performance
impact due to snapshots taken at any frequency of intervals.
And the networked storage solution has a built-in software
feature in order to recover from data loss.
Remote Site Disaster Recovery
The solutions described so far can only address data
protection and recovery within a data center or campus
environment. However, to protect against a data center
or site going down, as a result of events like earthquakes
and sabotage, customers should consider a more cost-effective
remote disaster recovery implementation.
The configuration options for remote site disaster recovery
vary widely depending on the distances between the sites,
level of redundancy required, and other policies for
In this type of configuration, storage at the primary
site uses mirroring technology to provide frequent incremental
updates of the data to the storage at secondary site,
which acts as the online backup repository for the primary
The active/active disaster recovery configuration is
similar to the active/passive configuration except that
the secondary site is also a production site. Just as
the primary site data is replicated to the secondary
site, the secondary data is also mirrored back into
the primary site with the help of mirroring software
for dual protection. This allows either site to recover
in case of a disaster at the other site. Each site also
continues to serve data to local clients.
In case of sites that are distributed over distances
larger than a campus or metro area, the backup configuration
requires the use of WAN links connecting the sites with
each other. These topologies highlight parameters like
QoS, security, cost of the WAN link, and whether the
link is dedicated for storage or is shared with other
types of voice or data traffic.
Security is always considered an important design parameter.
The topology might include IP firewalls, VPNs, or IPSec,
which act at the network layer, protecting and authenticating
IP packets between participating IPSec devices. These
design components may also require more consideration
in terms of application latency and response times.
Mirroring technology is highly efficient in its bandwidth
usage over the WAN links. The design involves transferring
only the incremental data at user-defined intervals
from the target storage to a Nearline storage
device. The incremental data is now archived to shared
If the WAN link is shared with other types of real-time
or latency-sensitive traffic, it is imperative to consider
network QoS at the network layer and look out for limitations
like throttle in the mirroring software.
Anal Jain, MD, India and SAARC, Network
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