ClearReplica 7.0 Overview

ClearReplica is a custom add-on to the IBM Rational Software ClearCase product. It provides geographically disjoint development as a less expensive alternative to ClearCase Multisite. ClearReplica provides many of the replication features of ClearCase Multisite as well as additional features. With ClearReplica you can replicate whole VOBs, "portions" of VOBs, a single or select files, a single or select branches, replicate multiple VOBs in to single VOBs, single VOBs to multiple VOBs and replicate VOBs to other VOBs within the same ClearCase region. These options allow more flexibility to create on-line backup VOBs and staging or distribution VOBs.

ClearReplica is licensed differently than ClearCase Multisite in that ClearReplica License pricing is not a factor of how many VOBs are replicated or the number of users of those VOBs. ClearReplica is licensed per location, therefore the cost is the same to replicate one VOB with one user from Atlanta to India as it does to replicate 100 VOBs with 300 users from Atlanta to India. Sites can in many instances replace hundreds of Multisite licenses with one or two ClearReplica Licenses. You simply need one license at each site if development is performed at both sites, or a single license at one site if the off-site location is just for backups or disaster recovery. This relaxed licensing results in huge upfront cost savings over traditional Multisite.

ClearReplica requires that ClearTrigger 10.3 or higher is installed at the sending and receiving site; again an unlicensed version of ClearReplica will suffice at the receiving site if no development is performed on the receiving VOB there.

Some restrictions that exist in ClearCase Multisite are relaxed in ClearReplica. For instance, developers can work on the "same" branch at both locations for there is no Multisite mastership restriction. Geographically disjoint development teams can still work on separate branches and this is still the recommended method.

Use ClearReplica for geographically distributed development teams or use it to provide a hot backup to recover lost versions in a fraction of the time. Use ClearReplica to automatically distribute code or binaries located in a directory in a VOB without having to use the bandwidth of replicating the whole VOB. Replicate portions of the VOB to teams all over the world or across the hall. Simply install and configure ClearReplica on top of a ClearTrigger installation and get started!

ClearReplica advantages over traditional Multisite

ClearReplica was designed as a low cost, but still feature-rich alternative solution to ClearCase Multisite so specific concerns of current and prospective Multisite users that were addressed. Some of them are outlined here:

• Cost and licensing – cost of entry

  ClearReplica is much more cost effective. Multisite is licensed per user of a replicated VOB so the cost increases when user and VOB usage grows, replicating a single VOB with Multisite that has 100 users in "Atlanta" and 30 users in "India" requires 130 licenses of Multisite, to start. ClearReplica is licensed per "location" so two licenses of ClearReplica and ClearTrigger are needed (one of each at each site). Doubling the number of users of Multisite replicated VOBs doubles the cost of "replication", while doubling the number of users of ClearReplica replicated VOBs adds no additional cost.
  
  

• Extended Transport Mechanisms (Added in 7.0)

  No need to open additional ports in your firewalls, ClearReplica can use any available transport mechanism with both automatic and manual options.
  
  

• Automatic Error Notification (Added in 7.0)

  You can have email automatically sent to one or more administrators when there are “Replication” errors or warnings.
  
  

• Parallel and distributed shippers and receivers

  You can run multiple ClearReplica Shippers and Receivers in parallel, even across distributed machines from heterogeneous architectures. This leads to fast performance for packet creation and processing.
  
  

• Enhanced Replication Flexibility

  ClearReplica allows more control over what is data is replicated. Multisite allows an organization to replicate a whole VOB from one ClearCase region to another region. ClearReplica allows you to replicate the whole VOB, a portion of the VOB, just a single file, or select branches if desired. No more chewing up corporate bandwidth replicating the entire development VOB when you actually desire to give the offsite location access to just a few directories. With ClearReplica you can actually "replicate" portions of many VOBs in one or more locations and place them together on a single VOB in another location. Replicate more often knowing you are only replicating the portion of the VOB you request get replicated. Now you can replicate to a partner/vendor the pieces from 20 VOBs and present the data to them as a single VOB. Replicate just the final product to a client from the development VOB without having to replicate "development" or create a separate VOB just to replicate the product.
  
  

• Extended “Deployment” capabilities to ClearCase

  Use ClearReplica “deploy” from ClearCase VOBs to regular flat file systems on local machines or remote machines around the world. ClearReplica “deployment” only requires the license at the “shipper” site. Now updates to a ClearCase VOB can be pushed as regular directories on countless machines making deployment of documents, web pages, patches, registry updates or even ClearCase triggers a snap. ClearReplica produces logs of what is sent and received so you know what has been deployed.
  
  

• Enhanced “Replication Triggers” allow further automation and notification to your “replication” or “deployment” process.

  Use ClearReplica “Replication Triggers” to automatically run scripts before or after either sending or receiving “Replication” packets. . Now you can use any in-house script to perform custom logging, send email notification, install/execute deployed files, lock VOBs or even redirect packets by just adding a ClearReplica replication trigger. ClearReplica has pre_ship, post_ship, pre_receive and post_receive triggers help you manage your distributed environment. No more checking log files for certain events, have them email you when events happen or have ClearReplica automatically perform the post deployment scripts. The destination machines do not even need to have ClearCase installed.
  
  

• Enhanced “Replication” and “Deployment” capabilities to disconnected machines or those without a static IP address

  ClearReplica facilitates the transfer of ClearReplica data between two ClearReplica servers that do not have direct access to each other, but share access to one or more machines between them that can be used as a ClearReplica 'proxy' machines. The machines used in the transfer that are not actually the source or destination ClearReplica Server constitute the 'proxy chain' of machines. ClearReplica can also facilitate the transfer of data between machines that do not have a static IP address (i.e salesman laptops) so that either “replication” or “deployment” data can be sent to those machines anytime they are connected to the web.
  
  

• Nearly free "disaster recovery", "backup sites" or "distribution hubs"

  ClearReplica "replication" to read-only VOB sites only require the license at the "shipper" site. ClearReplica requires the ClearTrigger and ClearReplica software at both the " shipper" and the "receiver", but if you are just replicating to the offsite location and no development is performed there, then ClearReplica Licensing is relaxed at the "receiver" site. Push to a web server across the country or a "backup server across the hall". Backup hundreds of VOBs to several locations or across the hall with only ONE ClearReplica license. A developer can access the "hot backup" VOB to see a version they just accidentally deleted in the "production" VOB and get the version without having to burden the corporate IT department.
  
  

• Works with ClearCase Lite.

  You can replicate VOBs created on a ClearCase Lite server if you need replication, but are not ready to upgrade to ClearCase from ClearCase Lite.
  
  

• Confirmation of packet delivery (automatic packet recovery)

  Before ClearReplica "ships" a packet to a location it gets confirmation from that location of the last successful packet processed. ClearReplica automatically adjust and sends all requested data "since" the last confirmed successful delivery. Dropped or lost packets are automatically recovered. Packets do not hang in the shipping bay waiting for you to reset epoch counters. Perform off-line maintenance on your VOB without worrying about missing packets other locations sent you, all changes will be sent automatically, the first time the location can communicate with each other.
  
  

• Relaxed Mastership

  ClearReplica has relaxed mastership. Users of ClearReplica VOBs can actually work on the "same" branch in different replicas and see each other's changes immediately. Now any of the "replica" sites can make an element because there is no mastership to get in the way of either site changing the /main branch to make the new element.
  
  

• Automatic data encryption

  All data packets sent via ClearReplica are encrypted and compressed.
  
  

• Relaxed Replica Management

  You can stop "sending" or "receiving" VOB packets at any time without having to "remove replica", a site can "opt-out" of replication at any time without having to coordinate with other replicas or worry about breaking other replicas because they had mastership of shared data. You can "opt-in" at any later time and quickly get back in sync or just choose to continue from the current point.