Open Source's Hidden Costs

Despite the benefits open source storage software offers, users need to establish what the hidden costs of open source storage software are, experts say. The major factors that affect the total cost of ownership are:

- Product installation and configuration documentation

- Product support

- Breadth of product functionality

- Hardware and software interoperability

One hidden upfront cost with open source storage software is finding documentation and scripts that ease its installation and configuration. Coraid's Kemp says, "The open source community is rich in information but it is a scavenger hunt to find exactly what you need."

Because of these concerns, commercial versions of Amanda, DBAN, and Openfiler available from Zmanda, Techway Services and Xinit Systems, respectively, provide documentation and install scripts for the commercial open source versions. Protocols like AoE are included with the Linux 2.6.11 kernel or bundled with hardware like Coraid's EtherDrive SR1520.

The costs for supporting open source storage software show up in different ways. Open source vendors are in general agreement that managing open source code and changes to it require, as a rule of thumb, administrators with at least two to four years of experience.

"Users who like the idea of modifying open source code need to take a close look at the code to make certain that they can work with it and that it is within their skill set to modify," Cambridge Computer's Farmer says.

Integrators like Terry Hull of the Network Resource Group (NRG) also encounter other issues with product support.

"Getting to the root of a problem when you have open source layer upon open source layer is rarely easy and the thing we (NRG) know we are giving up with open source storage software is a significant margin of management," Hull says.

Another major concern for open systems storage software is the depth of product functionality. Open source products like Amanda and OpenSMS, a policy-driven systems management storage software product, almost always have certain product restrictions. For example, Amanda will not backup Microsoft Windows hosts unless SAMBA, a file and print sharing utility, is first installed on the Windows host, and Amanda offers no media server option so all backups must go through a central server. OpenSMS only officially supports Linux 2.4 and 2.6 running on an XFS file system though it suggests it should work on other UNIX platforms and, with some porting, on JFS file systems. OpenSMS offers no integration with Microsoft Windows platforms.

The final major concern for enterprise shops is the lack of verifiable interoperability testing between the open source storage software and other hardware and software products in the user's environment. NRG's Hull notes that while interoperability is not a major concern for over 90% of his installs, he still never discounts the possibility of having to troubleshoot interoperability issues. Cambridge Computer's CTO Farmer says, "Unless the software has comprehensive support services behind it such as Amanda does, one needs a really good reason to mess around with it since primary storage is such a vital piece of the IT infrastructure."

Next Steps with Open Source

For the most part, open source storage software is still largely a work in progress that requires users to have years of practical experience as well as the time to research and support the products. However, there are initiatives under way to make it easier and more practical for users to deploy open source storage software.

First, vendors like Zmanda are helping to make a product like Amanda a more viable option for the average user. One of Zmanda's goals for the next 12 months is to simplify the install, configuration and management of Amanda so that it can be set up and managed by a novice or entry-level administrator.

Second, open source projects like Aperi are creating a standards based, open source software framework to manage storage networks. Standards like the Storage Management Initiative Specification (SMI-S) which defines a method for interoperable management in heterogeneous SANs that is now included with most storage software but provides users with no software to manage storage devices. Aperi goes the final mile and provides users with the needed open source storage software to manage storage that supports SMI-S.

In the meantime, Cambridge Computer's Farmer offers this advice:

1. Find an open source software where there is a large open source community and make sure that you have the skills and time to modify and manage the code.

2. Go with a low-cost solution with an easy way to migrate your data out if need be

3. Don't be afraid to pay an enormous premium for a big name vendor to avoid the risk