During its recent announcement on 1/18/2011, EMC revealed that it had delivered more than 10 Petabytes of SSD disk in 2010, and claimed the market lead. Not to be outdone, Fusion-io claimed it had shipped 15 Petabytes of enterprise Flash on 1/25/2011. Who is right?
Both vendors are correct; they compete in different marketplaces. There is some overlap, but that will decrease over time.
Storage Flash - SSDs
EMC was the first to announce flash storage drives (SSDs) in January 2008. The advantage of using the same disk drive form factor is that it can use the storage infrastructure and software. SSDs offer much higher IOPS and lower latencies (about 1ms or 10-3 seconds in the real world) than hard drives.
The original software support was at the volume level, and users had to select the volumes they wanted to put onto SSDs. At the announcement EMC joined most storage vendors who have now shipped support for moving parts of a volume (sub-volume or Sub-LUN support) onto the flash drives and have automated tiering software that will analyze usage patterns and automatically move them to an appropriate storage level. This allows a relatively small amount of SSD to be fully utilized and take most of the I/O activity, and this in turn allows lower performance and less costly drives to be used for the the rest of the data. The bottom line - lower cost of storage with little if any storage professional overhead. Overall latency remains about the same.
Some storage vendors offer read-only flash-cache as an extension of the storage controller. One vendor (FalconStor) offers a read/write flash-cache. These flash-caches are more expensive than SSDs but offer potential for more efficient use of flash for certain workloads. One of the most innovate recent announcements has been the Xiotech's hybridized storage, a combination of SSD and SATA drives within an integrated ISE (pronounced "ice") replaceable module. The IOPS and cost performance are impressive as is the 5-year warranty.
To put this into perspective, 10 petabytes of EMC flash compared with the ~15,000 petabytes of disk storage that were shipped in 2011 is less than 0.1%. Wikibon expects this to grow in excess of 10x over the next few years.
The speed difference between the processors and the storage remains huge. The SCSI protocol has to be both asynchronous and complex to deal with this speed disparity, with little prospect of improvement. As a result, the main value proposition of SSD flash at the storage level will remain one of reducing the overall cost of storage. One big advantage of the protocols is that storage can be shared across many servers.
Fusion-io is the leader in this space, both in petabyte shipments and software and hardware innovation. The main value proposition is as an extension of main memory that is both persistent (like disk storage but not like main storage) and with latencies measured in microseconds (10-6 seconds). The new VSL software framework announced by Fusion-io allows writes from the processor to flash in a single pass, making the software much simpler.
The main usage of server-side flash at the moment is to help databases and file systems perform much better. Locking rates are much higher, and completely new types of applications can be written that process an order-of-magnitude more data. Database servers with gigabytes of RAM and with terabytes of flash as an extension of RAM will become commonplace.
Server-side flash can also be configured as an SSD, with some performance benefits. The overheads of using a SCSI interface will still remain, but it can be more quickly deployed using standard software support.
One of the limitations of server-side flash is that the PCIe interface cannot be directly shared by other processors. However, there are cross-industry solutions on the product roadmap to address this limitation.
Fusion-io marketing has taken this opportunity to toot its own horn-- and why not? The company is growing rapidly and is one of the hottest startups on the planet right now in a domain that is disruptive and adds substantial business value to application owners.
Action Item: Horses for courses - choose the appropriate technology to solve the appropriate problem. SSDs will have very little adoption friction and will help reduce the cost of storage. Server-side flash has more adoption friction, but will have a much greater impact on the ease-of-use and functionality of software and a much improved user experience. Ask any iPad user.