Coraid Inc. today unveiled a storage virtualization appliance that adds logical volume management for pooling storage across its arrays, synchronous mirroring, snapshots, cloning
The VSX-Series SAN virtualization appliance works with EtherDrive SRX arrays that run the ATA over Ethernet (AoE) protocol instead of Fibre Channel (FC) or iSCSI to deliver block-based storage. The VSX appliance connects the EtherDrive SRX devices to servers to deliver data protection features to the SRX arrays.
AoE is a thin protocol layer directly on top of Ethernet that doesn't require IP or TCP layers. Coraid is the primary corporate backer of the AoE protocol, which was designed at Bell Labs and is an open-source community project. Coraid claims it has Ethernet SAN technology deployed in 1,300 customer environments, but CEO Kevin Brown admits the vendor has a long way to go before the protocol can be considered mainstream. He thinks the storage virtualization features provided by the VSX will help.
"Our biggest bottleneck has been lack of some of these features," Brown said. "That was the biggest gap that didn't allow us to compete in the enterprise. VSX is checking off some of those boxes."
According to Brown, "Some people say, 'Over my dead body, I'll never do anything different' when faced with AoE. With them, we move on," he said. "But we're finding that storage is becoming such a pain point and people are frustrated today. It will take a long time, but I think there's a strong movement. People want to move away from the monolithic old world to a more flexible, elastic cloud infrastructure." He said the U.S. Dept. of Defense is using VSX for a multipetabyte deployment.
VSX is a semi in-band device that works with any Ethernet switch that supports jumbo frames. Data requests go to the VSX and are moved to the SRX array, which returns the data to the servers via the switch. Responses are returned directly to the initiator. Brown said he expects most customers will be using virtual servers.
"By making it semi in-band, it makes it easier to scale out. It can scale out to petabytes behind two nodes," Brown said. "We're giving the customer a choice. They can do the advanced features with the hypervisor or they can do it in the array. They can choose. In some cases, the servers haven't been virtualized, so you would do the advanced features at the storage layer. We don't lock them in."
The VSX is compatible with Citrix XenServer, Microsoft Hyper-V and VMware hypervisors. Logical volume management lets customers build and re-size virtual volumes across storage shelves, and expand pools by adding EtherDrives. The device supports 4,080 LUNs, and can handle up to 256 snapshots per LUN. Snapshot copies can be made and modified without disturbing the original for testing environments. Writable snapshots, or clones, can be created to make modifications to the original data.
With the remote asynchronous replication, VSX maintains snapshot synchronization between local and remote logical volumes. The VSX buffers the WAN latency and tracks "dirty blocks" that still need to be replicated. The device ensures blocks that aren't replicated are delivered to the other side in case of WAN latency. WAN disruptions don't disrupt the application I/O and, upon WAN recovery the VSX will resume snapshot synchronization. For synchronous mirroring, the VSX maintains both copies in sync and writes to both copies. If hardware supporting one copy fails, the VSX provides continuous data access by using the other copy. Copies are automatically resynchronized after the repair.
George Crump, an analyst at Storage Switzerland, said the VSX box gives Coraid a true scale-out architecture. "While the server virtualization does allow all the arrays to participate in the retrieval of a discreet block of data, this gives Coraid a true scale-out design." Crump said. "Before, Coraid had to rely on the hypervisor or third party software. Storage virtualization definitely makes a difference in this context."
Crump said features such as snapshots, cloning and replication are expected in most storage systems these days. "Prior to this, Coraid depended on the operating system or the general environment. They would depend on the operating system or on VMware's hypervisor to do the snapshots," he said. "If you don't have these features, you have to expect people to ask why the system doesn't have them."