NAND Flash Memory - Enabling Mobility

Here's my presentation from the IDEMA Diskcon U.S.A. conference.

"NAND Flash Memory: Enabling Mobility"
Gregory Wong, Forward Insights
September 23, 2009
http://www.forward-insights.com/present/Wong-Diskcon_0909.pdf

Flash Memory Summit Presentation

My presentation "NAND Flash Memory Trends" at the Flash Memory Summit has been uploaded.

http://www.forward-insights.com/present/NAND%20Flash%20Memory%20Trends.pdf

A YouTube video of the presentation may be accessed at the following link.

http://www.youtube.com/watch?v=Kh02erRVna4

SandForce Unveils Revolutionary SSD Controller

SandForce has emerged from stealth mode and unveiled a SSD controller for enterprise and mobile applications. Key features of the SF-1000 controller include:

- Dramatically higher endurance (80x) due to extremely low write amplification – significantly lower than the WA of current SSD vendors.
- Symmetrical read/write 30k IOPS and 250MB/s sequential
- 5 year drive life with no daily write limitation for MLC SSD
- No degradation in the performance as the drive fills up
- No need for external RAM or over-provisioning thereby reducing system costs
- ECC engine and RAID configuration of flash devices provides unrecoverable BER of 10E17

Existing solutions trade performance, reliability and endurance at the expense of additional cost. SandForce's DuraClass technology offers better performance, endurance and reliability at a lower system cost and paves the way for use of MLC NAND in a tiered storage hierarchy in enterprise systems. If SandForce is able to deliver on its promises, it is a truly revolutionary technology which will help drive the adoption of SSDs in both enterprise and mobile environments.

WD Buys its Way into SSDs

Western Digital Corp., the 2nd largest HDD maker, announced that it had acquired SiliconSystems, Inc. for $65 million in cash. SiliconSystems is a major supplier of embedded SSDs to the network-communications, industrial, embedded-computing, medical, military and aerospace markets.

WD is no stranger to SSDs having dabbled in the technology in the early 1990's and being a founding investor of SanDisk which also developed flash-based SSDs in the same time period. However, it appears that early experience wasn't enough for a latecomer to catch up to the vast improvements in performance and reliability made by SSD vendors recently. System-level solutions particulary on the firmware side are required to manage the increasing complexities of NAND flash with each new technology generation.

WD is now able to leverage SiliconSystems' knowhow and IP to accelerate its development of SSD computing solutions. This knowhow combined with WD's branding and client relationships could make WD a formidable SSD vendor and validates the market opportunity provided by SSDs.

This acquisition will compel HDD suppliers to review their own internal development plans and may be the first with others to follow.

Fujitsu Next

Intel Corporation and Hitachi Global Storage Technologies announced that they will jointly develop Serial Attached SCSI (SAS) and Fibre Channel (FC) enterprise class solid-state drives (SSDs) for servers, workstations and storage systems. This is an exclusive agreement to develop and deliver SAS and FC enterprise SSDs with availability of the first products in early 2010.

This is a complementary partnership marrying Hitachi GST’s drive, channel and system knowledge together with Intel’s NAND flash and flash management expertise. Hitachi selected a strong NAND flash partner that doesn’t compete with it in its core HDD business. Now that two of the three enterprise HDD makers, Seagate and Hitachi, have publicly announced plans for enterprise SSDs, Fujitsu will be compelled to react, especially with its 23% enterprise HDD market share to protect.

Seagate may feel it is big enough to source the NAND flash and develop the SSDs on its own however, Fujitsu may need to develop a partnership with a NAND flash vendor. Two possible candidates: Micron and Hynix - NAND flash vendors with SSD ambitions but no competing HDD businesses. Micron has flash management expertise acquired through its own SSD development and leading cost structure based on 34nm technology. On the other hand, Hynix is lagging on both the SSD and NAND flash technology front.

If rumors of Western Digital acquiring Fujitsu's HDD business are correct, a company that has sat on the sidelines as companies have rushed into the SSD market will have to finally step up to the plate.

Seagate to Purchase SanDisk? Definitely, Maybe Not

Rumors are flying about Seagate buying SanDisk or Intel's stake in Intel-Micron Flash Technologies (http://www.eetimes.com/news/latest/showArticle.jhtml?articleID=210004140). Does it make sense? Seagate does need access to low cost NAND flash to fuel its SSD ambitions. Here are some ways to think about it.

1. If Seagate were to purchase SanDisk or Intel's portion of IMFT, what are they going to do with all that capacity? SSDs are not going to be able to eat up all that capacity, at least not for the next couple of years. Does Seagate want to manufacture flash memory cards or supply to MP3 players? SanDisk's operating margin in 2007 was 8% and Seagate's 6.8% in FY08. However, if you strip out income from royalties and licensing, SanDisk's operating margins were -5%. Combining a primarily OEM HDD business with a low margin retail business could be challenging.

2. Seagate is primarily interested in enterprise SSDs which uses exclusively SLC NAND flash technology. Any SanDisk acquisition provides Segate with 150k 300mm wafers per month of MLC NAND technology. Spending $4 billion (market cap of SanDisk) to obtain MLC NAND flash technology for enterprise SSDs? (SanDisk and partner Toshiba currently do not manufacture any high density SLC NAND parts, although that could change in the near future.)

3. Seagate spends almost $1 billion in capex ($930m in FY08) p.a. in their HDD business. SanDisk in 2007 spent roughly $1.6 billion and Intel $1 billion in NAND flash. Looks like Seagate's capex would have to at least double if it wants to become a NAND flash manufacturer and it's balance sheet would be strained supporting such a high level of investment.

4. Intel is not ready to exit NAND flash, at least not in the near term. IMFT has typically been behind the technology leaders by 1-2 process generations. With the 34nm announcement, they are about to leap ahead. With the technology lead, IMFT will presumably have the lowest costs. In addition, Intel will be releasing a slew of competitive SSD offerings in the next months. If, with the lowest costs in the industry and a very strong product lineup, Intel still can't make money, then it will consider whether it makes sense to be in this business, but they're not going to quit before giving it their best shot.

Seagate needs access to low cost NAND flash and they don't need to obtain that access by getting into the retail flash card business or doubling their annual capex. They could achieve the same means by either investing a small equity stake in a NAND flash vendor or placing an upfront payment to secure NAND flash capacity at preferential pricing. Apple did something similar when it introduced its first flash-based iPOD. Such an arrangement also affords Seagate sourcing flexibility especially if those wild hockey stick projections of SSD shipments don't pan out.

Finally! A Simple Metric for Solid State Drive Endurance

We've all seen the impressive MTBF (mean time between failures) specifications of SSDs versus HDDs of one to two million hours versus 600 thousand hours in a notebook pc class application. However, unlike HDDs where a mechanical failure can make the entire HDD unusable, the main failure mechanism in a SSD relates to the memory cells becoming unusable. MTBF is a statistical calculation that unfortunately, does not capture the effect of write endurance.

The write endurance of a SSD is a function of the type of flash memory used (SLC, MLC), storage capacity, frequency of writes, data sizes of the writes and the amount of static data which relates to the wear leveling algorithm. System level endurance of SSDs in the industrial, enterprise and miliary space have ranged anywhere from one million to five million program/erase cycles. There are three main problems with this.

1. The endurance will depend on how the SSD is used in the application. As a result, SSD vendors can tweak the parameters for their own marketing purposes.

2. Not all SSD vendors use the same formula for calculating the endurance and the formulas can be overly complex.

3. A straight endurance metric is nebulous and difficult to grasp its implications, especially for OEMs who've never had to grapple with endurance issues in HDDs. For example: What's the effect on the lifetime of the drive?

SanDisk aims to solve this with the Longterm Data Endurance (LDE) metric. LDE is simply defined as the total amount of data writes allowed in the lifespan of the SSD. The metric is based on the Bapco write usage pattern for a typical business user and assumes the data is written equally over the lifetime of the drive and that data is retained for one year once the LDE specification is reached.

LDE allows OEMs a simple way to compare SSDs and determine, based on the applications usage patterns which drives are suitable for a particular application. For example, a drive with an 80TBW (teraByte write) LDE can support 20GB writes per day for 10 years (equivalent to 73TBW). For an application requiring support for only half the number of writes per day (10GB), a 40TBW rated drive would be sufficient.

The beauty of LDE is that it captures endurance in one single, understandable figure. A common metric is necessary to facilitate SSD adoption moving forward. Now comes the hard part: garnering support from other SSD vendors and OEMs.

I've uploaded a copy of Don Barnetson's presentation on LDE, "Solid State Drives: The MLC Challenge" on my website at http://www.forward-insights.com/.

Samsung Introduces Server-Grade NAND flash for SSDs

Samsung Electronics announced today that it collaborated with Sun Microsystems to develop a SLC NAND flash memory with five times the endurance of conventional NAND flash memory. This would put the "ultra-endurance server-grade" flash memory at 500k program/erase cycles.

To extend the endurance, Samsung likely tweaked the underlying cell process and/or modified the programming algorithm. The net result is that the improved endurance comes at the expense of reduced performance or retention. However, by targeting high transactional enterprise applications with this device, the degraded retention should not be an issue.

Seagate Fires First Volley Against SSD maker

Hard drive maker Seagate a lawsuit against solid state drive manufacturer STEC in the Northern District of California claiming STEC infringed four of Seagate’s patents related to how a SSD interfaces with computers. This is the first time a HDD manufacturer has sued a SSD maker.

It’s hard to see the financial motivation behind such a move. STEC’s enterprise SSD revenues were only $11 million in 2007, although it could reach 4-10x more this year depending on the ramp of the ZeusIOPS and Mach8 MLC product lines. With a market share of over 50% in enterprise HDDs, Seagate clearly sees a longer-term threat from the leading maker of enterprise SSDs.

However, a bigger motivation would be to send a signal to flash memory makers about the value of its intellectual property. It’s no secret that Seagate has been courting NAND flash vendors to secure NAND flash for a SSD it’s planning for the end of the year. A rumored JV with Micron fell apart last year and it is apparently in discussions with two of the three largest vendors. One of the main stumbling blocks is what Seagate could bring to any cooperation as all NAND flash vendors have ambitions to develop and market SSDs. This litigation could be a validation of the IP which Seagate can offer. Western Digital, which along with Seagate, was an early investor in SanDisk (then SunDisk) apparently holds some critical controller and wear leveling IP and could be next to enforce its IP.

SanDisk is taking no chances. In Q2/07, it set up Solid State Storage Solutions LLC with unknown partners that will license IP, presumably SSD-related IP. In July 2007, Solid State Storage Solutions LLC invested $42.5 million for the acquisition of intellectual property. It has apparently purchased relevant SSD and controller IP from Renesas Technology. This IP could prove effective in extracting royalties from flash memory card manufacturers and controller makers entering the SSD space, but it is questionable whether it is enough to counter any future claims by Seagate and WD.