Tens of thousands of users are deploying open-source storage software in an effort to avoid pricey proprietary products such as array clustering and disk eraser applications and to get some long-term protection through the availability of source code.
Rafiu Fakunle, CEO of open-source vendor Xinit Systems, said that users have downloaded more than 38,000 copies of its Openfiler NAS and SAN software from the sourceforge.net Web site. And Zmanda -- the company providing support for the open source backup software product Amanda -- says that it supports 20,000 users worldwide.
Open source storage software is available to address a number of user needs, experts say. Amanda is a backup software product targeted at small and midsize businesses that allows the creation of a single master backup server to back up multiple hosts. DBAN (Darik's Boot and Nuke) allows users to securely wipe the hard drives of their computers.
Other open-source storage software includes Lustre, OpenAFS and SAMBA, which are each network file systems used for different tasks. Lustre is used in large scale cluster computing while OpenAFS is deployed to create a single file space across all computers so that any computer can access a file on any other computer. SAMBA allows Linux servers to provide file and print services to Microsoft Windows clients.
Integrators like the US-based Network Resource Group (NRG), say they can deliver substantial savings for their customers using open-source storage software. Terry Hull, a principal network engineer with NRG, recently put together a VLAN for a client using iSCSI and open source storage software.
"The incremental costs for the solution were US$1,500 for the open source software versus US$25,000 for a comparable configuration from Lefthand Networks and US$75,000 for a Dell Fibre Channel SAN," Hull says.
However experts remain skeptical about the wisdom of implementing open source storage software products. Jacob Farmer, the CTO of Cambridge Computer, has some clients who implemented OpenAFS and Lustre in order to avoid the high cost of clustered file system software from a company like TerraScale Technologies.
Despite Cambridge Computer's successes in deploying open sources storage software, Farmer says, "Only those with highly skilled personnel were able to pull it off. The rest found that these products were too complex and had deceptively high costs of ownership."
Key questions that users need to answer before using open source storage software are:
- What is open source storage software's value proposition?
- What products are available for their specific needs?
- How stable and scalable are the products?
- What risks do they present?
- Under what circumstances should an end users should consider open source?
- What level of user skill is required to implement and support them?
- What software support options are available?
Value Proposition
The three primary value propositions for open source storage software are:
- Minimal or no upfront software costs
- Comparable base line features as proprietary storage software products
- Availability of source code provides some level of long term protection
Open source storage software can be obtained in one of two ways - freely downloaded from a web site or purchased. For example, users interested in trying the open source Amanda backup software may either download a community edition from the sourceforge.net web site or purchase an enterprise edition from Zmanda's web site. While the underlying source code should be the same in both instances, Zmanda provides a 'sanity check' of the enterprise edition code ensuring that the version that the user downloads and installs is fully tested and compiled at their labs.
DBAN (Darik's Boot and Nuke) is an open source storage software product available in both free and commercial versions. DBAN meets the 5022.22-M standards of the US Department of Defense (DoD) for data erasure by overwriting all disk locations three times. Network Resource Group's Hull primarily supports Linux in his clients' environments and says he uses DBAN on a "constant basis to clean hard drives or partitions for my clients."
Other users like David Ritchie, an IT manager with an Atlanta-based staffing firm, still finds DBAN is not quite ready for his environment. With DBAN, which is often used on smaller servers with internal disk drives, Ritchie encountered some quirks when trying to erase data on volumes on external storage. "The amount of storage it displays is different than what is presented by the external storage array and the program runs single-threaded so you need to be strategic in how you deploy it," he says.
The AoE (ATA over Ethernet) protocol provides a method that is comparable to Fibre Channel for users to connect to external storage using common the 1Gbit/sec Ethernet protocol and network switches. As a registered IEEE protocol, AoE runs at lower level in the Ethernet stack than TCP/IP so it does not impact server performance in the same way that the iSCSI protocol does yet it provides approximately the same level of performance as more expensive Fibre Channel SANs. Coraid's CEO, Jim Kemp says, "On a 1Gb Ethernet link, AoE can achieve 110MB of throughput without burdening the host processor."
However, AoE does have a number of downsides. First, while drivers are freely available for Linux, FreeBSD and Solaris, Windows users still need to purchase an AoE driver such as Rocket Division Software's Starport software. Second, AoE is not a routable protocol so it can not be used to access storage on other segments of the LAN. Third, storage products that support this protocol are only available from a few vendors such as Coraid. Finally, AoE requires newer network switches that provide flow control that maximize throughput and limit network collisions.
The availability and accessibility of the source code is also a major advantage of open source storage software, especially for organizations that archive data for long periods of time. Charles Wegryzn, is a developer for Retriever Technologies in Santa Fe, N.M., which is working on an open source content management and digital archiving software. Wegryzn says it used to be fairly typical for users to buy software from IBM and IBM would include the source code inside. "Then Microsoft came along and changed everything. With open source, we are going back to our roots of how computer software sales used to work."
Cambridge Computer's Farmer thinks archived data is the single largest value proposition for open source storage software. Supporting proprietary data formats long term and the possibility of vendors going out of business who provide those formats are valid user concerns now. Farmer says, "With open source, at least you know you will have support in 25 years since you own the code."