SanDisk's Know-How
Strengthens the SSD Industry
With the goal of benefiting the end user experience, SanDisk
provides the technology and measuring tools to hasten the adoption
of solid state drives (SSDs) in PCs.
SanDisk's All Bit Line (ABL) architecture greatly boosts write
performance and reduces power consumption by uniquely sensing the
programming voltage in all word line cells simultaneously. Relying
on non-volatile flash, SanDisk's innovative nCache™ acceleration
technology1 utilizes system idle time to improve overall
responsiveness to user requests. SanDisk's flash management
technology, ExtremeFFS™, has the potential to accelerate the
performance and extend the endurance of SanDisk SSDs inside PCs
that use full-featured operating systems3. In addition,
LDE2 (Long-term Data Endurance), an industry metric,
introduced by SanDisk, quantifies how much data can be written to a
SSD in its lifespan expressed in terabytes written (TBW).
All Bit-Line (ABL) NAND
Architecture
SanDisk's patented All Bit Line (ABL) NAND architecture vastly
improves write performance and reduces power consumption in the
SanDisk® SSD G4 series of solid state drives.
Relative to conventional memory architectures, SanDisk ABL
architecture boosts write performance and utilizes highly
effective, advanced algorithms to achieve these outstanding
results. Such algorithms exercise all cells in a selected word line
simultaneously, immediately sensing the programming condition of
non-volatile storage elements. Less sophisticated architectures use
every other cell in a consecutive rather than a simultaneous
process. SanDisk ABL architecture reduces power consumption due to
its efficient even and odd bit line voltage sensing.
Non-Volatile Write Cache
(nCache™) Acceleration Technology1
All HDDs and many SSDs use a DRAM write cache to allow the drive to
quickly receive and acknowledge write commands back to the system,
taking advantage of system idle time when the user is not waiting
for responses. But the DRAM write cache does not always live up to
this expectation. Since data in DRAM is at risk from a sudden power
loss, full-featured operating systems force the drive to flush the
cache whenever it contains critical information. Windows can issue
FLUSH CACHE commands as often as 30 times per second when the
system is busy, greatly limiting the effect of the DRAM write
cache. SanDisk's innovative nCache™ acceleration technology is a
large, non-volatile write cache. As soon as data is written to the
SSD, it is stored in non-volatile NAND flash that saves data
reliably even in the absence of power. With no volatile cache, the
SSD is not subject to the performance penalty associated with FLUSH
CACHE commands.
SanDisk nCache™ acceleration technology frees the write cache to
operate as intended. It quickly receives and acknowledges writes
back to the system in the background, when the user is not waiting
on his system, to maximize system responsiveness.
ExtremeFFS™ (Extreme Flash
File System) Technology
ExtremeFFS Technology has the potential to accelerate random write
performance thus extend the endurance of SanDisk® G4 SSDs inside
PCs that use operating systems such as Windows® XP and Windows®
73. Based on SanDisk's TrueFFS™ flash management system
that was introduced in 1994 and incorporated into Windows 95 as a
leading flash file system for major mobile handset vendors,
ExtremeFFS™ applies a novel approach to flash management based on
design elements such as:
- Page-based algorithm: Customized for popular operating systems
such as Windows® Vista, Windows® XP, Windows® 7. ExtremeFFS
technology uses a page-based algorithm with no fixed coupling
between physical and logical location. This gives SanDisk SSD G4
the freedom to store a sector of written data where it is most
convenient and efficient.
- Fully non-blocking architecture: NAND channels operate
independently as required by user activities, with some reading
while others are writing and garbage collecting.
LDE (Long-term Data
Endurance) 2
LDE is the first industry metric that expresses how long data can
be reliably stored in SSDs in a measurable number. LDE was proposed
by SanDisk as a benchmark to enable users to compare the data
endurance of SSDs from various manufacturers. Based on typical
end-user activity, LDE provides the total number of data writes,
expressed in Terabytes (TBW) that can be performed over the SSD
lifespan.
Footnotes:
1 nCache™ acceleration technology is a large Non Volatile Write
Cache, a unique feature in SSD P4 that improves random write
performance and ensures an improved user experience. Studies show
that modern operating systems mostly access the storage device
using 4k access blocks. The cache is filled during these small
write commands and emptied during idle time when the host is not
accessing the drive, with no risk of data loss. For a typical
everyday use, the write performance that the users see is the
nCache™ (burst) high performance, and not steady state (sustained)
SSD P4 performance. Based on IOmeter 4K random write test.
2 Approximations based on LDE
(Long-term Data Endurance) - an industry metric, introduced by
SanDisk, that quantifies how much data can be written to a SSD in
its lifespan expressed in terabytes written (TBW). Data is written
using typical PC transfer size , written at a constant rate over
the life of the SSD and data is retained for at least 1 year upon
LDE exhaustion. Based on SanDisk internal measurements, a typical
client PC user writes 4GB/day
3 ExtremeFFS™ is a SanDisk
page-based flash management algorithm, optimized for popular
operating systems, has the potential to greatly increase SSD random
write speeds and efficiency thus accelerating the performance and
extending the endurance of SSDs inside PCs