EMC Centera Virtual Archive Planning and Configuration

White Paper
EMC CENTERA VIRTUAL ARCHIVE
Planning and Configuration Guide
Abstract
This white paper provides best practices for using EMC Centera
Virtual Archive in a customer environment. The guide starts with
an overview of Virtual Archive and discusses typical use case
scenarios, performance considerations, scalability/sizing, and
network latency.
May, 2013
Copyright © 2013 EMC Corporation. All Rights Reserved.
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of its publication date. The information is subject to change
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herein are the property of their respective owners.
Part Number h6905.2
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Table of Contents
Executive summary.................................................................................................. 4 Audience ............................................................................................................................ 4 Terminology ....................................................................................................................... 4 Virtual Archive ......................................................................................................... 5 Federation .......................................................................................................................... 5 Virtual Archive software ...................................................................................................... 5 Host System ....................................................................................................................... 6 Member System ................................................................................................................. 7 Campus Federation ............................................................................................................ 7 Virtual Archive Recommended Configurations .......................................................... 7 Applications ....................................................................................................................... 7 SDK and XAM Versions ....................................................................................................... 7 Application Behavior .......................................................................................................... 7 Specific Applications .......................................................................................................... 8 Sizing ................................................................................................................................. 8 Number of Access Nodes ................................................................................................ 9 Number of Management Nodes ...................................................................................... 9 Cluster Size .................................................................................................................. 10 Network and Latency ........................................................................................................ 10 Bandwidth ................................................................................................................... 11 Network Address Translation (NAT)............................................................................... 11 Location of application servers and the Host System .................................................... 11 Campus Federation ...................................................................................................... 11 Replication and Failover ................................................................................................... 13 Replication in a Federated Environment........................................................................ 13 Failover in a Federated Environment ............................................................................. 15 Use Case Considerations ....................................................................................... 15 Supported Use Cases ....................................................................................................... 15 Capacity Expansion ...................................................................................................... 16 Use Cases Not Supported for a Virtual Archive .................................................................. 20 Virtual Archive in a WAN setup ..................................................................................... 21 Direct connectivity to a Member System in a federated environment ............................ 21 Conclusion ............................................................................................................ 21 EMC Centera Virtual Archive
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Executive summary
EMC Centera® Virtual Archive is a new EMC technology that enables the aggregation
of a set of EMC Centera clusters. This set of clusters forms a virtual, tamper-proof
archive with the capacity of all clusters aggregated and available to applications.
Once connected to the Virtual Archive, EMC Centera functionality will be accessible to
applications in a seamless manner. Capacity and processing power can be added
beyond the existing boundaries of a single EMC Centera system or a single data
center.
EMC Centera Virtual Archive allows customers to federate multiple Centera systems to
create a single, highly scalable, distributed digital archive. Most significantly, the
EMC Centera Virtual Archive simplifies management of archives at scale and distance,
delivering significant operating efficiencies and flexible allocation and reallocation of
archive capacity.
Audience
This white paper is intended for technical pre-sales personnel who have a good
technical background and understanding of storage technology. Familiarity with the
existing EMC Centera components, concepts, and features is essential and
recommended.
Terminology
The following table summarizes the commonly used terms used in this guide.
1
Terms
Definitions
ARM
Advanced Retention Management feature of EMC Centera
BLOB
Denotes the finite bit string that is the customer data. A single C-Clip™ can
contain pointers to multiple BLOBs. The content of a BLOB is opaque to
CentraStar®. BLOBs also have associated Content Addresses, but they are
not exposed to the applications accessing EMC Centera. This is to ensure
the path to the data is always through the appropriate pointer (C-Clip)
Centera SDK
Centera Software Development Kit
Centera Viewer (CV)
Management tool used for EMC Centera configuration
Centera Virtual Archive
A collection of federated clusters with Virtual Archive software
Centera Virtual Archive
software
The Virtual Archive software that is hosted on one cluster on multiple
cubes/nodes
Cluster
A cluster consists of one or more EMC Centera cubes interconnected to
present a single storage array
Cube
A single EMC Centera unit containing a minimum of four and a maximum of
321 nodes including a set of cube switches
EMC CentraStar
EMC Centera firmware running on the Centera hardware
EOSL
End of Service Life
Federation
A collection of clusters either acting as a Host or Member System that
GEN3 or older clusters have 32 nodes in a cube. GEN4 and GEN4-LP clusters have 16 nodes in a cube.
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together form a virtual archive
Federation Source
The Federation in a replication configuration that sends data to a remote site
Federation Target
The Federation in a replication configuration that receives data written to the
Federation Source by the application(s)
GEN4-LP
Generation 4 Low Power Centera hardware
Host System
A cluster that executes the Centera Virtual Archive software
Member System
Any cluster in a Federation that is eligible to store and retrieve content and
does not host the Virtual Archive software
Replication Source
The primary cluster in a replication configuration that sends data to a remote
cluster
Replication Target
The cluster in a replication configuration that receives a copy of the content
written to the primary cluster by the application(s)
Restore Source
The cluster where restore is started, from which content is copied to a
specified restore target
Restore Target
The cluster that receives a copy of the content from a cluster running restore
LAN
Local Area Network
VIM
Vendor Interface Module
WAN
Wide Area Network
Table 1. Terminology
Virtual Archive
Virtual Archive is designed to provide customers the ability to address increasing storage
demands by adding more EMC Centera storage in an effective manner. Virtual Archive
addresses the need to expand archives into other data centers and increases the abstraction of
the technology to also include software versions and other architectures. The latter is needed to
ensure seamless access to a long-term archive and to deal with the unknown (not-yet-known
new storage technology).
Virtual Archive is software-based and can be configured to run on any GEN4-LP running EMC
CentraStar version 4.0+. Virtual Archive allows for scalability of EMC Centera clusters up to 512
nodes.
This section covers the main components and concepts of Virtual Archive used
throughout the guide.
Federation
A Federation is a collection of clusters that together form a Virtual Archive. It is
comprised of a single Host System and one or more Member Systems. After the
Virtual Archive software is installed on standard EMC Centera GEN4-LP hardware, an
EMC Centera service representative will need to perform the process of creating the
Federation on the Host System and then adding additional Member Systems.
Virtual Archive software
Starting with CentraStar 4.2.2 the Virtual Archive software is part of the CentraStar
software. The CVA routing software takes the responsibility of routing data traffic
between the Host and Member Systems. When a request is received from an
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application server(s), the Host System decides which system in the Federation will
service the request. The request is then routed back via the Host System to the
application server(s).
Figure 1 shows the Virtual Archive data flow in a federated environment comprised of
a Federation of a Host and a Member System.
Note: Applications will always need to connect to the Host System regardless of its
location.
Figure 1. Virtual Archive data flow
Host System
A Host System is the cluster in a Federation on which the Virtual Archive software is
configured to run. The routing software gets installed on all nodes in the host
systems. The CVA software is active on all nodes that have access and management
roles. Applications connect to the Federation through the Host System. Virtual Archive
software smartly routes and balances the application data streams across all clusters
in the Federation, including itself, based on load distribution, capacity distribution,
available capacity, and the nowrite state of the cluster.
With the release of Virtual Archive 1.1, the Host System can be either a new or
existing GEN4LP cluster. There is only one Host System supported in a Federation.
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Member System
A Member System is any cluster in a Federation that is eligible to store and retrieve
content. Member systems must be running CentraStar 4.1 or later.
Campus Federation
A Campus Federation is comprised of data centers that are interconnected and
accessible via a LAN. Virtual Archive Host and Member Systems need to be located
within certain proximity. In a Campus Federation, latency, packet loss, and bandwidth
should all be taken into account.
Virtual Archive Recommended Configurations
This section provides a summary of the recommended best practices that should be considered
when deploying Virtual Archive.
Applications
One of the key factors to consider when deploying Virtual Archive is the set of applications to
be used in the customer environment. Virtual Archive has been designed to work seamlessly
with EMC Centera integrated applications, but some caveats do apply.
SDK and XAM Versions
Virtual Archive supports EMC Centera SDK version 3.1 and later, as well as version 1.0 patch 3
of the EMC Centera SDK for XAM (also known as EMC Centera VIM). This means that all
applications to be used with Virtual Archive must be integrated with these or later versions.
Note that the vast majority of applications are integrated with EMC Centera SDK version 3.1 or
later; however, in some cases, an upgrade to EMC Centera SDK or EMC Centera SDK for XAM
(Centera VIM) may be required.
Application Behavior
Although Virtual Archive supports all Centera SDK and XAM functionality, there are a few
additional considerations.

SDK considerations
EMC Centera Virtual Archive has been designed to take advantage of protocol
improvements introduced in EMC Centera SDK 3.2 and Centera SDK for XAM 1.0
patch 3. For this reason, the latest version of Centera SDK and Centera SDK for
XAM should be used, when possible.

Large datasets
When using EMC Centera SDK 3.1 with Virtual Archive, if the Host System is
unstable, for example, access nodes are unstable or bounce, then transactions
with datasets greater than 2 GB may not complete successfully. In this
scenario BLOBs may end up in different Member Systems and need to be
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moved to a single Member System that has the CDF stored. Having a CDF and
BLOBs on the same Host or Member System is known as co-location. During colocation of large BLOBs the SDK may time out, thus resulting in a failed
transaction. Therefore, in order to use Virtual Archive in such situations it is
recommended that the application(s) upgrade to EMC Centera SDK version 3.2
or ensure that the Centera is in a healthy state.
Specific Applications
The following applications have been identified with specific problems areas, if deployed with
Virtual Archive.

Bus-Tech MAS
The MAS device is integrated with EMC Centera SDK 3.1 and is known to write
and extend large datasets. In order to use Virtual Archive with this application
it is recommended that the application use EMC Centera SDK version 3.2 or
later.

OpenText LEA
In order to use Virtual Archive it is recommended that the customer use
standard EMC Centera replication for solutions requiring replication and avoid
using STORM ISO Device Manager Application replication.

CommVault QiNetix Suite
This application is integrated with EMC Centera SDK 3.1, and is known to write
very large datasets (up to 2 GB). These transactions may not complete
successfully if the Federation is under heavy load. It is recommended that the
application use EMC Centera SDK version 3.2 or later.

EMC Centera Universal Access (CUA)
In order to use CUA in a Virtual Archive environment it is recommended that
CUA version 4.1.1 be used. CUA 4.1 or later will use EMC Centera SDK 3.2,
which is the recommended SDK version to be used with Virtual Archive. CUA 4.0
and older versions use a version of SDK earlier than 3.2.
Note:
For any recommendations or clarification regarding application usage
with Virtual Archive, please contact CenteraVirtualArchive@emc.com .
Sizing
Many factors influence sizing and the scenario could vary for different customer environments.
Factors influencing the sizing decision may include, but are not limited to, the following:
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
Application load

Total number of access, storage, and management nodes required on a Host System

Number of open pool connections by the applications

Number of applications accessing the EMC Centera system.
These factors are discussed in this section.
Number of Access Nodes
The number of access nodes on a Host System should be planned carefully. The cluster that
hosts the Virtual Archive software requires at least the same number of nodes with access roles
as found on a Member System(s) in the Federation. If an application is designed to open up
many pool connections to the EMC Centera (going beyond the recommended best practice of
25 connections per access node) and has a high volume ingest and retrieval rate, then with the
introduction of Virtual Archive, the number of access nodes should be increased on the Host
System to match the Member System(s).
Table 2 summarizes the access nodes sizing of a GEN4-LP for the Host System based on the
number of access nodes that were on the Member System(s).
GEN4-LP
Centera
# Nodes
# Access Nodes
Member System 1
16
2
4
6
8
Member System 2
16
2
4
6
8
Host System
16
4
8
82
82
Table 2 Host System – Access node sizing
When installing Virtual Archive in EMC Centera storage environments that have multiple
applications and/or high ingest rates, for example, consolidating multiple applications to use a
single Federation, it is recommended that a Host System with a large number of access nodes
be used. This will allow customers to have an equal or better performance experience after they
have installed Virtual Archive.
Number of Management Nodes
Virtual Archive software uses management nodes for the purpose of keeping the Federation in
sync. Multiple management nodes should be configured on each Host and Member System for
redundancy. A minimum of two management nodes are recommended on all systems in the
Federation.
2
A maximum of eight access nodes are allowed on a 16-node EMC Centera.
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Cluster Size
In order to choose the Virtual Archive Host System cluster size users should look at the
following areas:
1. Application load
2. Number of applications
3. Content protection scheme

Application load
An important factor to consider when sizing an environment for Virtual Archive
is the application load and number of applications. Ingest and retrieval rates
could vary from one application to another. Therefore, understanding
application load helps assess whether the EMC Centera cluster is being used
most effectively.
If Virtual Archive is used as a means of adding more capacity, then the number
of access nodes may need to be increased to get the same or better
performance for the existing applications and application load. The same sizing
rules as for a single Centera cluster apply in this case.

Content protection scheme
EMC Centera offers two protection schemes, Content Protection Parity (CPP) and
Content Protection Mirroring (CPM). CPP stores six data fragments and one
parity fragment and CPM stores four objects (two BLOBs, two CDFs) on two
unique nodes. A minimum of an eight-node configuration is required for CPP
and a four-node configuration for CPM.
As a standard best practice, applications having small objects use CPM and
applications having large object sizes use CPP. However, Virtual Archive will not
elect a Member System based on file size. It does not enforce any restrictions
on the protection scheme selection and it is not required that the Host and
Member Systems have the same protection scheme. Best practice
recommendations for having a CPP or CPM cluster should be followed according
to application recommendation.
Note: More information about capacity and protection schemes is available in the
white paper EMC Centera Capacity Reporting for Gen4LP on CentraStar 4.0 - A
Detailed Review available on http://www.emc.com and http://powerlink.emc.com.
Network and Latency
As a general networking concept poor network connectivity can increase latency and packet
loss. High bandwidth utilization can also affect the application ingest, retrieval and query rates.
This section provides best practices recommendations on how to avoid network issues for
Federation in a campus environment.
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Bandwidth
The network between the clusters in the Federation must accommodate the
application write, read, and query requests to the Federation in a campus
environment. This means that the network between the clusters in the Federation
must support the aggregate bandwidth required by all applications. The best practice
for Federations with high application loads is to support twice the aggregate
bandwidth required by all applications.
Network Address Translation (NAT)
EMC Centera Virtual Archive does not support the use of NAT between Host and
Member Systems that are federated. If NAT is used, all Member Systems must be on
the same logical side of the NAT boundary.
Location of application servers and the Host System
EMC Centera is an IP-based device and uses an IP network for connectivity of its data
operations. As of CentraStar 4.2.2 the Virtual Archive is installed with the CentaStar
software but must be configured to run via the CentraStar CLI. For more information
on how to configure the system please reference the CentraStar 4.2.2 user’s manual.
Applications will connect only to the Host System as it is responsible for making sure
that data is routed between systems in the Federation and application servers.
Therefore, general network design practices to keep latency low and avoid packet
loss and congestion apply.
Campus Federation
With Virtual Archive it is recommended that the application servers, Host System, and
Member Systems be located within a company campus on the same network. If not,
performance issues could arise due to latency and packet loss introduced by
additional network hops. Figure 2 shows an example of a Campus Federation whereby
all the application servers, the Host System, and Member System are located within
the same data center and interconnected via a single LAN switch.
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Figure 2. Campus Federation

Virtual Archive and LAN
Within a Campus Federation it is possible to have the Host and Member
Systems located in different data centers provided there is acceptable LAN
connectivity.
Figure 3 shows the scenario where the application servers and Host System are
located in data center A, and the Member System is located in data center B.
However, since all components are located in the same location and
interconnected via LAN, this configuration meets product specifications.
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Figure 3. Federation in a multi-LAN environment
Replication and Failover
Virtual Archive allows content to be replicated in uni-directional and bi-directional topologies.
Virtual Archive requires a one-to-one mapping of a primary Federation to a replica Federation.
Inward star and chain replication topologies are not supported in Virtual Archive environments.
The following scenario explains the requirements for setting up replication in a federated
environment with Virtual Archive.
Replication in a Federated Environment
In order to set up replication in a federated environment an EMC Centera service representative
needs to make sure that the Federation Target site has an equal number of clusters. The
available capacity for clusters on the Federation Target can be equal to or greater than the
clusters on the Federation Source site. There needs to be a one-to-one mapping between the
Federation Source and Federation Target site clusters. Figure 4 gives an example of how
replication would look in a federated environment.
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Figure 4. Virtual Archive setup in a uni-directional replicated environment
In Figure 4, replication needs to be set up between Alpha and Charlie (Host Systems at the
Federation Source and Federation Target sites, respectively) and between Baker and Delta
(Member Systems on the Federation Source and Federation Target sites, respectively).
However, when setting up replication between Alpha and Charlie, an EMC service
representative needs to make sure that the correct data port is used. Virtual Archive software is
installed and uses the data port 3218; therefore, port 13218 should be used when supplying
the Federation Target address for replication shown in
Figure 5:
Config# set cluster replication
Replication Enabled? (yes, no) [no]: yes
Replication Address: 10.241.44.19:13218,10.241.44.20:13218
Failover Address [10.241.44.19:13218,10.241.44.20:13218]:
10.241.44.19:13218,10.241.44.20:13218
Replicate Delete? (yes, no) [no]:
Profile Name: replication
Location of .pea file [prompt]: C:\replication.pea
Config#
Figure 5. Replication setup on a Host System using CLI
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Failover in a Federated Environment
Failover in a federated environment is different from the traditional EMC Centera SDK failover.
The failover IP address is set manually on the Host System by using the CLI command
federation set failover.
Figure 6 shows configuration of a failover address on a Host System.
Config# federation set failover
Federation failover enabled (yes, no) [no]:yes
Failover address [not set]: 10.241.44.19:13218,10.241.44.20:13218
Issue the command?
(yes, no) [no]:yes
Config#
Figure 6. Virtual Archive failover setup using CLI
If the Federation Source is inaccessible for any reason, the EMC Centera SDK will fail over to the
Federation Target. Failing over to the Federation Target only takes care of reads (writes do not
fail over). This is shown in Error! Reference source not found.
Figure 7. Federation failover scenario
Use Case Considerations
Supported Use Cases
This section provides information on the typical use cases that are supported by Virtual
Archive.
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Note: To discuss use cases not listed in this section please contact
CenteraVirtualArchive@emc.com.
Capacity Expansion
This section will discuss the use cases where Virtual Archive can be used as a means of
expanding capacity for EMC Centera systems that are at four racks.

Adding Capacity to an Existing Cluster
Customers often face the need to increase the storage capacity of their
existing EMC Centera clusters, which they do by adding more EMC Centera
storage to their existing environment. In most cases they expand capacity by
adding additional nodes to their existing clusters, but if there is a need to
expand to multiple cabinets they now have the option to use Virtual Archive.

Steps for adding Virtual Archive in an existing environment
Capacity can be added to any cluster in the Federation that is at four racks.
When using Virtual Archive as a means to federate existing clusters and add
more capacity it is recommended that the new cluster runs the Virtual
Archive software. Once the Federation is established, additional new
clusters or nodes can be added. The steps to add capacity by using Virtual
Archive are outlined next:
1. Configure the new cluster to match the configuration settings of the
existing cluster environment. This means that all clusters must run the
same compliance mode. If the Host System is running in basic
compliance mode and the Member System is running GE than the Host
System must have the GE license.
The Cluster Configuration Sync Tool can be used to determine
differences between the Host and Member Systems.
2. Configure the Virtual Archive host system on the new or existing cluster.
Refer to the release notes for the CentraStar version supported by Virtual
Archive and the CentraStar user’s manual on how to configure the CVA
and router software.
Note: Clusters in a Federation do not have to be at the same CentraStar code
level.
3. Create a Federation on the Host System.
4. Add a new or existing Member System to the Federation. You must use
the Cluster Configuration Sync Tool to merge pools and profiles to the
Federation.
5. Update the application connection string so that it now uses the Host
System IP.
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Figures 8 through 10 describe the process of adding capacity to a new or existing Host System
and then adding the existing EMC Centera cluster as a Member System.
Figure 8. Customer environment before adding Virtual Archive
Figure 9. Adding a Host System and creating a Federation
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Figure 10. Existing EMC Centera cluster added to a Federation as a Member
System

Adding capacity by using Virtual Archive in an existing environment (replicated setup)
In the scenario where a customer is adding capacity using Virtual Archive
and has an existing replicated setup either in uni- or bi-directional
replication, a Federation needs to be created at the primary and replica
sites.

Steps for adding Virtual Archive in a replicated environment
The following steps need to be followed in order to add capacity to the
primary and replica sites by using Virtual Archive:
1. Configure the new or existing cluster at the primary site to match the
configuration settings of the Member Systems, using the Cluster
Configuration Sync Tool.
2. Install Virtual Archive software on the new or existing cluster to be the
Host System at the primary site or the Federation Source.
3. Create a Federation on the Host System and add new or existing clusters,
up to three, to the Federation.
You must use the Cluster Configuration Sync Tool to add Member
Systems to the Federation.
4. Perform steps 1 through 3 for the target site or Federation Target.
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5. Establish replication between Host Systems at the Federation Source
and Federation Target using the CLI command set cluster
replication. Use port 13218 when setting up replication between
the Host System at the Federation Source and Federation Target sites
and provide a failover address. This is shown in
6. Figure 11.
Config# set cluster replication
Replication Enabled? (yes, no) [no]: yes
Replication Address: 10.241.44.19:13218,10.241.44.20:13218
Failover Address [10.241.44.19:13218,10.241.44.20:13218]:
10.241.44.19:13218,10.241.44.20:13218
Replicate Delete? (yes, no) [no]:
Profile Name: replication
Location of .pea file [prompt]: C:\replication.pea
Config#
Figure 11. Replication setup between Host Systems at Federation Source
and Target
7. Repeat step 5 for all the Member Systems.
8. Update the application connect string so that it now uses the Host
System IP at the Federation Source.

Federating two existing or new clusters
Virtual Archive supports federating two to four existing clusters. Using the
Cluster Configuration Sync Tool you can synchronize the existing clusters to
match cluster configuration settings. These settings include:

Pool and profile settings

Compliance

Retention
Steps to federate existing clusters include the following:
1. Install Virtual Archive on one of the existing clusters that will become the
Host System.
2. Create a Federation on the Host System.
3. Add the second existing cluster as a Member System.

Clip Invariant support
Clip Invariant is the process by which Virtual Archive ensures that it keeps
only one instance of a clip found on more than one Member System in a
Federation. A clip can exist on more than one cluster due to any of the
following conditions:

The existing clusters in the Federation at one time were a replication
pair.
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
Restore operation was performed on any of the clusters in the Federation
and that resulted in having the same clip existing on more than one
cluster.

Data was manually copied by EMC Service or a customer to a different
cluster and that resulted in having the same clip exist on more than one
cluster.
In the scenario where a clip resides on more than one Host or Member
System in the Federation, upon receiving any data read or update request
for the particular clip, Virtual Archive reads the Write Time Stamp (WTS) of
all occurrences of the clip. It will then update the clip having the lowest
delta between the cluster time and the WTS. Note that all other occurrences
of the clip are marked invalid by setting their WTS to a sentinel value. The
sentinel value is set at the file system level and clips with WTS marked to a
sentinel value will not be read on any future requests. Figure 12 shows the
process flow for Clip Invariant scenario.
Figure 12. Clip Invariant process flow
Use Cases Not Supported for a Virtual Archive
The following use cases are not supported.
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Virtual Archive in a WAN setup
Virtual Archive software is not suited for any clusters that are geographically dispersed; that are
in different cities, states, countries; and that require a WAN-to-WAN connection. Going over the
WAN can add huge network latency and packet loss and could potentially result in a degraded
performance. It is therefore not a supported use case to have Virtual Archive in an environment
where the Host System, Member Systems, and application servers are dispersed across
different cities, states, or countries connected by a WAN.
The next figure shows an example of a configuration that is not supported and should be
avoided.
Figure 13. Virtual Archive connectivity via WAN is not supported
Direct connectivity to a Member System in a federated environment
In a federated environment, the application servers should always connect to the Host System.
The Host System is the only cluster that has knowledge about the Federation and therefore is
responsible for the routing of data transactions. If application servers connect directly to the
Member Systems for data operations the application will not be able to read data that was
routed by the Host System to Member Systems.
Conclusion
This configuration guide is intended to provide recommended configurations for EMC Centera
Virtual Archive. It is expected that after reading this document the reader will have a better
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understanding of where this technology can be deployed in customers’ existing environments
and the various factors that need to be considered.
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