Multi-pathing software is considered such an integral component for delivering high availability, load balancing, path failover and path management that few organizations can envision deploying a server on a FC or iSCSI SAN without having this software in place. But for such a critical piece of software, multi-pathing software still has its detractors. Among their complaints is the lack of availability of a multi-pathing software solution with no strings attached.
Broadly speaking, multi-pathing software can be divided into three (3) buckets:
- Storage system vendor provided multi-pathing software. Storage system providers often make available their own multi-pathing software that works on a variety of operating systems. The upside of using their multi-pathing software is that it often has features that take advantage of advanced features on their storage array.
The catch is that their software only works with their storage systems (or possibly a limited number of storage systems from other providers) so creating heterogeneous storage environments is NOT feasible.
- Operating system vendor provided multi-pathing software. The exact opposite is true when using the native multi-pathing software found on operating systems. This software is handy in that it is often included for free with the OS plus it supports heterogeneous storage environments and works with any vendor’s storage system.
The downside with using this software is that it only works on that OS so each OS has its own multi-pathing solution. This becomes problematic from a support perspective as organizations need to verify that all storage systems work with the multi-pathing software from each OS they have in use.
Further, there is no management software that I am aware of that enables administrators to centrally manage all of these disparate multi-pathing solutions. This forces administrators to log into each server or management console for each OS to manage each multi-pathing solution.
- Symantec Storage Foundation with Dynamic Multi-Pathing (DMP). DMP has always been the Cadillac of multi-pathing software solutions in that it is both operating system and storage system agnostic. Organizations could deploy DMP on almost any OS and use it with nearly any storage system as it supports over 1000 models at last count. DMP can also be centrally managed across all of these different servers using Veritas Operations Manager.
The main knock on DMP to date was that in order to use it organizations also had to install Symantec’s Veritas Storage Foundation and the Veritas File System (VxFS). Installing these additional layers was not always possible or practical on existing application servers since they could not always justify their deployment in order to use DMP.
Symantec’s decision to decouple DMP from its parent Storage Foundation puts that concern to rest. Currently, a standalone version of DMP is available for Solaris, AIX and Red Hat and SuSe Linux. Beginning in Q4 2010, Symantec will also make DMP available as a standalone product for HP-UX and Windows. This now frees customers to deploy DMP without a requirement to first deploy Storage Foundation or VxFS.
In talking to Symantec, its internal testing reveals that to install this standalone version of the DMP software will take about 15 – 30 minutes per server for two reasons.
- First, most organizations are already running some form of multi-pathing software. Organizations will need to install DMP onto a server, take the existing multi-pathing software out of the environment and then complete the switch to DMP.
- Second, multi-pathing software like DMP is a kernel application so a reboot is required. The length of the downtime for individual applications will be a combination of the time it takes to install and configure DMP and then reboot the server.
A true heterogeneous solution that worked across both server and storage environments has always been largely restricted to DMP. However the one concern that users raised – the requirement to first deploy Veritas Storage Foundation and the Veritas File System (VxFS) – has limited DMP’s broader adoption in many environments
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Symantec’s decision to decouple DMP from Storage Foundation and make it a standalone product removes that objection of some detractors. Now DMP provides organizations a multi-pathing software solution that offers support for nearly every OS and storage system that they may have.
But even as Symantec removed the strings requiring organizations to deploy Storage Foundation in order to use DMP, what was equally as important is that it left in place the strings that organizations want DMP to have. Users may still leverage Symantec’s freely available Veritas Operations Manager to centrally discover and manage all of the DMP implementations across servers in their environment. In so doing, organizations gain the advanced visibility and reporting about that they want in their multi-pathing environments while removing one of the last objections that they may have to its deployment.