Last December the Centera group announced the delivery of the Centera Virtual Archive. The CVA release is primarily about scale: multiple Centera systems can now be aggregated using federated software. Federation was implemented in two areas: on the data path and on the management path.
On the data path side, any request to read, write, query, and delete objects would be sent to one Centera, and that Centera would cooperate with the others in the virtual archive to execute the request.
On the management side a similar approach was used. CAS configuration requests (e.g. create virtual pool, create retention class) are received by one Centera and coordinated across all of its peers.
There are a lot of interesting algorithms that have to be in place in order to give the appearance of one enormous petabyte-scale object archive. Perhaps I can discuss these algorithms in future posts.
At a very high architectural level, however, a quick look under the hood of CVA reveals a brand new piece of software: the CAS Router.
CAS Router High Level Description
The CAS Router software has two main differences when compared to the embedded Filepool software that has been running inside Centera for years. In the first place, the CR is written in C++ (Filepool is written in Java). Secondly, it is not necessary for the CR to run on every single Centera node (Filepool runs on every node in a RAIN architecture).
When the Centera Virtual Archive software is installed, the CR can be thought of as a federated proxy that intercepts data path and management path requests.
Although it is not implemented as a filter driver, the genesis of the CAS Router idea has its roots in the layered architectures of products such as PowerPath and CLARiiON.
Benefits of the CAS Router Architecture
There are a number of things that I like about this approach:
- Quality: Federation is a complex feature to implement, and using a CAS Router approach minimized any impact on the existing Filepool code. The Filepool software has been hardened to the point where the data from the field has elevated Centera to an availability level of 5 9s. Implementing Federation in the CAS Router means that Filepool was not significantly changed (which could have introduced new defects). It is also true that customers who do NOT want the scale of a Centera Virtual Archive are unaffected by the new Federation software.
- Choice: Going forward the Centera team now has two choices when it comes to implementing new features. Depending on the feature, it might make sense to enhance Filepool, or it might make sense to enhance the CR. The choice of language (C++) is particularly relevant here. If Centera wants to integrate a new technology, the implementation of that technology may be available in only one programming language. Java technologies might best be integrated into Filepool; C/C++ technologies might best be integrated into the CAS Router. Which leads to the final benefit…..
- Innovation: I’ve written before that innovation can often be accelerated via combining adjacent technologies. Any time a “filter driver” architecture is introduced into a system it allows for value added services to be inserted. I can envision a whole new set of internal proposals that leverage the CAS Router’s ability to “store and forward” CAS requests. Can I insert the Atmos C++ client API into the CAS Router? Sure. Can I log CAS traffic and dump the results to an RSA enVision audit log device? Yup. Can I call out to an RSA key server and perform encryption in the same way that the PowerPath layered architecture does it? Definitely.
One new area that I see the CAS Router enabling is the ability to participate in automated vendor-neutral migrations. XAM technology promises that objects can be seamlessly migrated between XAM-compliant XSystems. Each object is exported from a system into a vendor-neutral, canonical format before it is imported into a different XSystem. For example, researchers at Penn State are working with HP on XAM research. In theory the CAS Router could be used to automatically migrate objects back and forth between two XAM systems.
As each new version of Centera software rolls out it typically comes with a statement about new levels of scale. The Centera Virtual Archive announcement was no different, but the software itself also includes a new piece of technology: the CAS Router.
Steve
http://stevetodd.typepad.com
Twitter: @SteveTodd
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