Exclusive: Intransa realizes dreams of 10Gb iSCSI
StorStac PCU100 combines superior performance, scalability, and manageability
Notably, the clusters provide automatic failover. If one controller fails, the other controllers continue to make the storage available to the same hosts. In testing, I ran IOmeter against a partition on the StorStac, then disabled one of the two controllers. There was a short (15 second) delay during switchover, but the IOmeter job continued to run without interruption or error. Controllers don't load balance automatically; with one LUN (logical unit number), there's no gain in performance if you've got two controllers. Multiple LUNs can be spread across two or more controllers, providing the same 500Mbps to 700Mbps performance to each, and file systems can stripe across multiple LUNs for doubled performance.
The controllers are all managed through a single virtual IP address. Conveniently, all the storage is addressed through that IP address, regardless of how many actual controllers there are. You can set up more then one IP for segregation of storage, but it isn't necessary.
There's also a single management interface for all controllers, offering excellent, easy-to-use monitoring of all hardware as well as configuration and management of RAID levels and other software functions. Each partition can have different RAID levels, numbers of drives, and stripe sizes, and these settings can be saved as a policy and applied to new partitions as well. You can also easily expand LUNs in size as desired -- without downtime.
Current supported RAID levels are 0, 1, 10, and JBOD(just a bunch of disks), with RAID 6 coming soon. The RAID 10 that Intransa uses can handle multiple drive failures, as long as two drives in the same pair don't fail simultaneously. If a drive fails, an unused drive is automatically added to the defined partition, and rebuilding takes place automatically. Rebuilding occurs at about 50Mbps -- even while the array is in use.
Adding hosts that are allowed to use the controller is also simple. The controller will register any host attempting to connect to storage. Through the management interface, an admin can then grant access, with one click, for any LUN defined on the system.
Finely tuned features
The system's replication features are what you'd expect, including cloning (mirroring), snapshots, and asynchronous replication. The latter, of course, doesn't require a WAN gateway, since it's already occurring via TCP/IP. Intransa also adds some OS-specific and extremely useful functionality. On Windows, the Intransa system integrates with Microsoft Volume Shadow Copy for snapshots through the OS. On Linux, iSCSI devices (/dev/sda, /dev/sdb, etc.) usually are not persistent – if you have more than one iSCSI LUN attached and reboot the Linux server, the devices may change positions and thus designations. Intransa drivers rename the devices using the LUN name from the controller to prevent this.
The Intransa StorStac PCU100 offers serious speed at accessible pricing. Intransa does not sell directly, but through individual partners who set the pricing. According to Intransa, a basic 10Gb system with one controller and one 4TB drive shelf should start at about $75,000; about $130,000 with 24TB. A dual-controller system with 24TB should cost about $180,000.
This is a fair chunk of change, but not more than a 4Gb FC solution; the cost of host adapters and switches for 10Gb Ethernet should continue to fall more rapidly than 4Gb FC. The Intransa StorStac PCU100 delivers the performance level you'd expect from high-end storage and ease-of-use is great. Expanding the system with more controllers or storage is a snap, plus you can combine 1Gb, 2Gb, and 10Gb controllers with the same disks. Although the PCU100 is not the ideal solution for databases and other transactional systems that need high numbers of IOPS, it's an excellent solution for streaming data at very high speeds or aggregating a whole lot of smaller streams.