Coraid binds storage and open source

For some people, having "storage" and "open source" in the same sentence may sound like an oxymoron, but by the end of this column, I'm hoping their opinion will change.

First, let me give credit for this week's column topic to Keith Goettert, who is CIO and account executive at the Island Power Program at Ecology Energy. As you can probably guess from its name, Ecology Energy offers environmentally conscious solutions to creatively extracting energy from a variety of sources.

It's tempting to digress on the clean energy topic, but to get back to storage -- after reading "A challenger for ISCSI," Goettert remembered his conversations with Coraid and, sensing a possible similarity between the two, sent me a note.

What's Coraid up to? Coraid's flagship product, the EtherDrive Storage Blade, is essentially an intelligent board that mounts and connects a single ATA drive to detached servers over Ethernet. Coraid ships as many as 10 blades in a single rack-mountable 3U shelf and, interestingly, allows customers to use their own drives.

Multiply the size of your favorite ATA drive by 10, and you have a target shelf with remarkable capacity, as much as 4TB. Stack a virtually unlimited number of shelves, and you can now attach a gargantuan amount of storage to your Linux or FreeBSD servers.

"What?" you may ask, "No Windows?"

"It takes more effort to build drivers and graphical interface for Windows," says Coraid CEO Jim Kemp. However, he adds that support for Windows will follow when market conditions will justify its development.

Customers can download drivers from the Coraid Web site, but since January Linux drivers have become an integral part of the 2.6 kernel. Those drivers make each EtherDrive-mounted disk appear as a local physical drive. Just use your imagination -- and standard tools such as LVM (logical volume manager) -- to shape those terabytes of storage in a variety of RAID clusters, suitable for a variety of applications.

Needless to say, those Linux drivers exploit the servers' NIC cards, but what's on the blade side? Essentially, they mount a Tibco processor, some memory, an Ethernet 10/100 card with RJ45, and an ATA connector to the drive.

In a typical implementation, your servers would have GbE for performance, and you would attach each EtherDrive shelf to an Ethernet switch with 10/100 ports and GbE uploads.

If you think this is beginning to look like, smell like, and walk like iSCSI, well -- no, it isn't. The only similarity with iSCSI (and other IP storage solutions such as Zetera's) is the Ethernet medium; the open source protocol that Coraid uses -- AoE (ATA over Ethernet) -- does not use IP and is not routable.

A non-routable protocol can be a blessing or a curse, depending on your requirements. If you only need to stuff your server-ducks (pardon, Penguins) with tens of TBs of storage, Coraid would probably love to hear from you. However, if your storage networking ambitions stretch far beyond physical-layer connectivity, AoE alone could be a tight jacket. "Our protocol is complementary, not in competition with iSCSI," Kemp says.

Let me close with a clarification: To be accurate, Coraid and Zetera have more in common than just the Ethernet medium. In fact, both approaches also make the humble disk drive a smarter and more flexible device, capable of standing in a storage network on its own merits and without intermediaries. It may be too soon to say, but that aspect could be what makes both so interesting and could prove to be the ultimate reason for their success.

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