Getting the absolute maximum performance from Flash-based storage and providing shared access across multiple servers typically requires a solid state storage appliance. These systems are designed specifically to eliminate bottlenecks and latency to deliver extreme performance. However, most of these systems were not designed to provide enterprise-level high availability (HA), and if that capability was needed, workarounds had to be implemented.
The lack of HA functionality in the past could often be overcome if the SSD appliance was used by a single application. In these cases, the application software could often provide HA. For example, Oracle can provide HA through its ASM software. Because it is a single application the method is uniform and relatively easy to operate.
For mixed application environments, especially those involving server virtualization, providing HA becomes more challenging and the functionality needs to be delivered through hardware. Thanks to virtualization technologies, the number of scenarios in which mixed applications and workloads need to have access to a high-speed solid state memory appliance is increasing rapidly. As a result, the number of data centers that could benefit from the extreme high performance of a solid state appliance is also increasing. Few storage solutions eliminate virtualization’s ‘I/O mixer‘ problem as effectively as a solid state storage appliance.
This combination of factors led Texas Memory Systems to develop the RamSan-720, their first solid state storage appliance with complete high availability in the box. The RamSan-720 is available in either 6 or 12 TB capacities and uses SLC Flash memory for maximum reliability and durability. Unlike other systems that have tried to fill the high availability void Texas Memory also kept power consumption in check, as the appliance only requires 300 to 400 watts.
A key feature of the RamSan-720 is that it has no single points of failure. Being highly available without the need for additional software makes it ideal for virtualized server or virtualized desktop environments. It has a new two-dimensional Flash RAID technology, completely redundant components, hot-swappable Flash Modules, and as stated earlier, runs on very little power.
The 2D Flash RAID works by having Variable Stripe RAID (that Storage Switzerland covered in the article “SSD, Heal Thyself”) inside each Flash Module as well as system-level RAID that goes across Flash Modules. RamSan-720 systems include twelve Flash Modules, and when system-level RAID is enabled, ten are used for data, one is used for parity, and one is used as a hot spare. This provides complete data protection as well as sparing in the event of failure.
The RamSan-720 provides four layers of data correction. First is system-level RAID 5 (as mentioned above), managed by centralized RAID controllers, which protects against module failure. Then there is the module-level Variable Stripe RAID, which protects against sub-chip, chip, or multi-chip failures on the Flash Module. Then there’s also a module-level RAID 5 in which each module provides data protection across its own chips, once again protecting from chip failure. Finally, there is chip-level ECC, which corrects bit and block errors.
Combined, the four-layer data protection strategy not only makes the RamSan-720 the most reliable Flash system created, but it may be the most reliable storage system created. Certainly it’s one of the most well-protected.
To complete the HA picture, the RamSan-720 uses completely redundant components eliminating single points of failure at the sub-system level. All the Flash Modules have redundant data ports which connect to redundant controllers, redundant I/O interfaces, crossbar switches, data buses, RAID controllers, power supplies, power paths, clock circuits, and batteries.
From a performance perspective the RamSan-720 packs a lot of punch in its 1U chassis. It can produce 400,000 IOPS (using 4K blocks) and can transfer data at 5 GB (bytes not bits) per second making it ideal for high-bandwidth environments. It has latency of less than 100 µs and four I/O ports for connectivity, either Fibre Channel or InfiniBand.
Storage Swiss Take
Texas Memory Systems can no longer be thought of as “the quiet little company from Houston, Texas”. The RamSan-720 could put them in direct competition with legacy primary storage manufacturers. Their thin software stack makes them an ideal complement to virtual environments where the hypervisor can provide much of the data services’ functionality as we outlined in the recent video “The Storage Hypervisor”.
Leveraging the hypervisor’s capability to migrate virtual machine image files without disruption, the RamSan-720 can be seamlessly placed into a virtual server environment. Then, as virtual machines need I/O performance, those VMs can be migrated in real time to the RamSan-720. Hence, in these environments we see the RamSan-720 not as direct competition to the traditional disk-based storage systems but more of a complement. With the RamSan-720 in place, the immediate performance requirements of the most demanding virtual machines can be handled by live migrating them to it, and the other virtual machines can continue to be served from traditional storage systems.
Migrating these demanding virtual machines from the hard disk system should also lighten the load on that system and allow it to provide better performance to less demanding virtual machines. For data centers looking to augment the storage system supporting their virtual infrastructure instead of replace it, the RamSan-720 should be given strong consideration.
Texas Memory Systems is a client of Storage Switzerland