Texas Memory's 2D Flash RAID incorporates chip-level RAID within each flash module and centralized system-level RAID striping across all flash modules. This dual-RAID functionality ensures protection and repair of any data contained on failed chips or modules, and is implemented in redundant hardware to eliminate bottlenecks.
In addition, the system employs redundant data paths from the external SAN interfaces, through dual system-level RAID controllers, to dual-ported flash modules to protect data against component failure. Redundant power is achieved through the use of two AC power units and three battery units. Each board in the Ram-San 720 is powered by two independent power rails. If AC power is lost, batteries facilitate saving all user data and metadata to flash as part of an orderly shutdown operation.
All this high availability may sound like overkill, especially in an all-solid-state system, which is generally more reliable than a mechanical disk array. Consider, though, the types of applications the Ram-San 720 is targeted to--transaction-intensive database applications, financial services applications, military applications, and large virtual desktop implementations. Customers using the applications need high performance without the risk of a single point of failure causing downtime.
The Ram-San 720 joins several other all solid-state appliances in the high-availability sweepstakes. Among those appliances are the Violin Memory 6000 Series, the Kaminario K2, and the DataRam XcelaSAN, along with the hybrid Nimble CS series, Tintri 540, and XIO Hyper ISE, which use both flash and conventional hard disk drive (HDD) technology.
Each appliance has differences in implementation. In the all-solid-state drive (SSD) category, Texas Memory has included all of the high-availability features in a single 1U box and, at 12 TB, provides a very dense solution.
Violin packs the same useable capacity into a 3U box with fully redundant components and has a multi-level cell (MLC) version with 22 GB of useable capacity. The larger size does provide user access for hot-swapping Violin's VIMM flash modules and other redundant components, like fans and power supplies.
Kaminario, in contrast, can scale in both capacity and performance, with user choices for DRAM or flash for performance storage, and HDD or flash for backup storage. In the Kaminario K2, multiple IO director nodes and multiple storage nodes are required for high availability and can be configured based on performance or storage capacity. A typical installation will be in a 42U rack that includes an uninterruptible power supply (UPS).
DataRam, on the other hand, achieves high availability by providing dual XcelaSAN units of 256 GB each, with a mirroring function.
In the hybrid arena of devices that include both SSDs and HDDs, the Nimble CS series provides dual hot-swappable controllers, mirrored NVRAM and power supplies, and up to 36 TB of raw HDD and 12 TB of raw SSD used as a cache, all in a 3U package.
The Tintri 540 is targeted specifically at VMware applications and features dual controllers, redundant power supplies, 2.4 TB of SSD and 24 TB of HDD, all hot-swappable, into a 3U package.
XIO has a 3U package with dual controllers and 6.5 TB of SSD and 10.4 TB of 10K rpm serial-attached SCSI HDD.
These are all very high-end devices with big price tags, and are typically deployed in business-critical applications that require 24/7 operation. In these uses, the importance of high availability, self-healing, all with hot-swappable redundant components, is that a single point of failure is not acceptable.
The Ram-San 720 is expected to be available by the end of January 2012 for $20,000 per TB.
Deni Connor is founding analyst for Storage Strategies NOW, an industry analyst firm that focuses on storage, virtualization, and servers. James E. Bagley contributed to this story.
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