SandForce's revolutionary SSD controller
Equivalent and fast read 'n' write speed
Major storage OEMS are expected to release commodity NAND chip-based flash memory products this year based on a new SandForce controller offering fast and symmetric read and write speeds, 80 times more endurance than notebook flash, and peak performance maintained for five years.
SandForce is a newly-visible fab-less startup. It has announced its SF-1000 SSD (Solid State Drive) processor family, and it's presenting itself as fully capable of supplying enterprise-class SSD controller functions better than any existing enterprise SSD product supplier such as Fusion-io, Intel, STEC, TMS, and Violin Memory.
It was founded by current CEO and president Alex Naqvi in June 2006 and based in Cupertino. The idea was to design a single system-on-a-chip (SOC) to control a solid state drive composed of ether single-level cell (SLC) or multi-level cell (MLC - 2-bit) commodity NAND chips and, by clever processor design, provide faster speed, longer endurance, lower power, and better data integrity than any other enterprise NAND flash SSD supplier.
There have been two funding rounds. The B-round was completed in February this year, with "total funding north of twenty million," according to Naqvi, from two venture capital firms, Storm Ventures and Doll Capital Management, now DCM, as well as "Tier-1 storage companies." Who might they be?
Naqvi reckons there are around ten top tier storage companies. Likely candidates could include EMC, HDS, HP, IBM, NetApp, Seagate, Western Digital, possibly Sun, maybe LSI. Two or more of them would appear to be SandForce investors.
In February 2008, SandForce licensed Tensilica's Diamond Standard 108Mini RISC controller core to use in its storage controller chipset designs.
SandForce has since moved to Saratoga, with a 15,000 square foot headquarters lease, and it has slightly more than 50 employees. The chief technology officer CTO is Radoslav Danilak who comes from NVidia and has a number of patents filed. The firm's VP of engineering, Amaresh Kumar, also comes from NVidia.
The SandForce controller's performance is stated to be 30,000 IOPS and 250MB/sec with either reading or writing of 4KB data blocks. This read-write symmetry is most unusual in the NAND flash world. Also, the read and write performance of 250MB/sec seems fast. Look at SuperTalent: Its MLC-based MasterDrive RX has a maximum sequential read speed of 230MB/sec and a maximum sequential write speed of 160MB/sec. Its SLC MasterDrive RX does 230MB/sec reading and and has a 200MB/sec maximum sequential write speed. SandForce must have some secret sauce here.
Typically flash writes take longer than reads because the write operation has to be preceded by a delete operation. Has SandForce found a way to do deletes in the background so that a write can be completed in a single operation?
One of Danilak's patents refers to using compression to increase performance in a data storage system.
The controller is coupled with a hardware compression/decompression engine. Compressed data is stored in a particular, primary region of the data storage device with any overflow data in a mapped overflow region. When read the decompressed data is stored in the host server's DRAM with the DRAM location stored in a table along with the storage device address, the pair constituting a pointer linking the DRAM address to the storage device address.
This appears to mean that, if there is a write request for the DRAM data, then it can be written at once to the storage device address. If no pointer exists then data in DRAM is written via a read-modify-write sequence, which takes longer.
System performance is increased as a result of data compression because less information is written to, and read from, the (storage device). Two more of the Danilak patents deal with compression.
The DuraClass technology of the SF-1000 is claimed to offer its longer endurance (compared to, say, Mtron and Phison notebook SSD controllers), up to 100 times more reliability than other SSDs and better power efficiency with 5,000 IOPS/watt (compared to a stated less than 20 IOPS/watt for hard drives) without using either a DRAM cache, over-provisioning the flash or requiring a stated or de facto daily write limitation to achieve endurance goals.
SandForce says users will experience five years of MLC SSD life with no daily usage restrictions. It reckons that both Intel M-class SSDs and Fusion-io ioDrives have effective write limitations.
Reliability is aided by its own error correction logic and by using RAISE, a Redundant Array of Silicon Elements, which is said to be single drive RAID-like but more efficient. (Having a 'redundant' array does suggest some kind of over-provisioning). Data written through the SF-1000 controller is automatically encrypted by the chip's hardware.
SandForce provides a 3Gbit/s SATA interface to the SF-1000 although a SAS interface is available from partners supplying a SATA-SAS bridge. It also has a SMART interface for diagnostics. The company says that, because it has a single chip controller, it can be used, uniquely, by OEMS to build a 1.8-inch format 512GB SSD, 512GB being the maximum capacity the controller supports.
Its roadmap extends to shrinking NAND geometries, 3 and 4-bit MLC technologies, adding a 6Gbit/s SATA interface plus PCI Express, USB 3.0 and other interfaces.
SandForce says it is engaged with multiple tier one SSD OEMs and its SF-1000 product will be shipped later this year.
Perhaps it's significant that Mike Desens, IBM Systems and Technology Group VP for system design, is quoted in SandForce's release: "The SF-1000 SSD Processor Family promises to address key NAND flash issues allowing MLC flash technologies to be reliably used in broad-based, mission-critical storage environments. These innovations can be truly disruptive and will accelerate the adoption of Solid State technologies across the data center."
Desens has been heavily involved in IBM's Big Green eco-friendly initiative and has been quoted with reference to IBM's million IOPS project Quicksilver which used 4TB of Fusion-io SSD. Fusion-io seems confident in its IBM relationship so perhaps IBM will use SandForce-controlled SSDs somewhere else in its product range, but in a data centre environment. Could SSDs, which first appeared in mainframes in 1978 (StorageTek 4305), be about to return to them?
There are two other potential SSD OEM connections visible at SandForce. Dr. Chong Park is a SandForce board director and also a board director at Seagate, which has publicly said it will enter the enterprise SSD market this year but has no known SSD technology relationships except with LSI.
Before joining SandForce, Kent Smith, SandForce's senior product marketing director, was the product management director at SATA multiplexer chip maker SiliconStor, which he and the management team sold to LSI in February 2007. Michael Vorhis, Sandforce's applications engineering director, also worked at SiliconStor in the period leading up to the LSI acquisition.
It appears that Intel, Fusion-io, Texas Memory Systems, STEC, and Violin Memory have a potentially substantial new enterprise SSD competitor, with existing storage OEM relationships about to bear fruit. SandForce appears well-funded and well-staffed, with credible storage OEM relationships. Its claimed capabilities regarding MLC flash - both read-write speed and symmetry, prolonged endurance, and data integrity - are far in advance of any other enterprise SSD supplier and are, it says, equally applicable to notebook use.
This means that, as MLC flash cheapens the cost per GB of SSD storage, SandForce's controller technology could help make it applicable to many more use cases currently best-served by hard disk drives. The company and its technology is now out of stealth, giving people a chance to see how both stack up and whether or not SandForce will be the actual force in the enterprise and mobile SSD markets it claims to be. ®