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, AFM, has the potential to accelerate the performance
and extend the endurance of SanDisk SSDs inside PCs that use
full-featured operating systems3.
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 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.
Endurance
Metric
SanDisk developed the first industry metric (previously known as
LDE) that expresses how much data can be written to a SSD during
its lifespan in a simple, accurate and relevant number. The metric
specification was developed by SanDisk and submitted to JEDEC as a
benchmark to enable users to compare the data endurance of SSDs
from various manufacturers. Based on typical end-user activity, the
metrics provides the total number of data writes, expressed in
terabytes written (TBW) that can be performed during the SSD
lifespan. Data is written using typical PC transfer size
distribution of writes, written at a constant rate over the life of
the SSD and data is retained for at least 1 year upon TBW
exhaustion. A typical client PC user writes 4GB/day, based on
SanDisk internal measurements.
1 nCache™ acceleration technology is a large Non
Volatile Write Cache, a unique feature in SSD P4-P2 and S2 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.