White Paper
Using DuraWrite™ Technology to
Accelerate Flash Performance and Extend
Write Lifetimes on the Nytro™ WarpDrive™
Application Acceleration Card
Overview
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Accelerating applications can be
enabled by using flash storage,
however performance can depend
on flash management techniques
Using a patented and patentpending technique, DuraWrite
technology is designed to
provide significant performance
improvements over typical
enterprise flash offerings
Utilizing the compressibility of
typical financial and database data,
DuraWrite technology allows less
flash writes to occur which extends
the lifetime of Nytro WarpDrive
acceleration cards
Most enterprise applications have demanding performance requirements and flash storage
technology is being used to enable users to achieve these performance requirements by
reducing application response times. Having no mechanical delays that limit hard drive (HDD)
performance, flash storage is a breakthrough for demanding customers. Not all flash products
are equal because the demanding environment of datacenter use requires extraordinary
flash management. This paper discusses how significant acceleration is possible from the LSI®
SandForce® flash processor implementing DuraWrite™ technology. This patented and patentpending architecture is designed to increase transaction performance and extends the life of
the flash accelerator card over typical flash management algorithms.
Steps Required to Store Data on Flash
Writing data to flash storage can be a several step process which often limits transaction rates
and response times. Since data cannot be directly overwritten on flash, old data must first
be erased, after which new data may be written. The process by which the SSD reclaims the
physical areas that no longer have valid data is called “garbage collection”. This process requires
consolidating valid data from a flash block, writing it to a different block, and then erasing the
original block which then removes the invalid data and frees up the space it was consuming.
Compounding this requirement is “write wear” on the flash device. This characteristic of
flash limits the number times the flash can be rewritten. Many SSD controllers claim to have
improved “wear leveling” to maximize the endurance of the flash, however wear leveling is only
going to ensure that every flash block has the same amount of writes when the SSD reaches
the maximum number of writes across the drive. The SandForce flash processor obtains the
maximum number of writes by using the proprietary and advanced DuraWrite technology to
actually reduce what needs to be written to the flash.
Performance Gain
Transaction Performance Improvements
using DuraWrite
Mitigating Flash Limitations with DuraWrite
As described above, writing to flash memory requires many necessary
steps. Each step adds more delay before a write can be completed,
70%
60%
and the more data that is written, the greater the delay. The
50%
40%
DuraWrite technology works on the principal of reducing the amount
30%
of data needed to be written through intelligent lossless compression
20%
10%
0%
10% compression
50% compression
30% Write / 70% Read Transactions
White Paper
techniques. Using the “white space” or otherwise redundant information inherent in most data,
sometimes as little as 50% of the actual data will need to be written to the flash. This yields
roughly a 50% reduction in the amount of data written. This translates into a significant boost
in performance. The following graph shows the relative performance improvement that can be
expected based on the compressibility of data.1
Oracle® Database Application
The Oracle database is an extremely common enterprise
application that helps automate business processes and analyze
data quickly and efficiently. To get an idea of a typical entropy level
of an Oracle dataset the Developer Days prebuilt virtual machine
image was used. This virtual machine is available from the Oracle
Technology Network and has Oracle Enterprise Linux and Oracle 11G
R2 installed with a sample database for hands-on-labs. Running the
83 MB “example01.dbf” database through gzip to get an idea about
the compressibility is illustrated in Figure 2.
Over 70% of the space2 is saved by compressing the database file.
Looking at a dump of the original data file at a random location
in a text editor helps explain why this level of compressibility is
achievable. The dump is illustrated in Figure 3.
Figure 2
Database applications apply a structure to the data that is stored in
the database. This defines the types of data, applies formatting limits,
and defines the relationship between various kinds of data. The data
is then stored in a format that makes it easy to find a specific piece
of information and update it quickly. From the data dump above it is
easy to how the data is stored with text fields that are easily readable
and a repeating metadata storage structure data. The emphasis on
speed of data retrieval and update over economy of space leads to
the high compressibility that is easy to observe. Even in applications
where compression is used within the database to put emphasis on
the economy of space, a 10-20% compression ratio is still possible
due to the compressibility of the metadata structure around the
compressed data.
Microsoft® SQL Server Database Application
Figure 3
MS SQL is another very common enterprise application. The internal
details and management interface are completely different than Oracle, but the properties
of the stored data that it creates exhibits similar properties. In the figure on the next page is a
dump from part of a data file that was created for a TPC-E test.
Using DuraWrite™ Technology to Accelerate Flash Performance | 2
White Paper
space provides more room for the SandForce processor to more
efficiently manage the “garbage collection” steps. Normally an SSD
controller will end up writing more data during garbage collection
causing “write amplification”. In hard disk drives, write amplification
is 1.0 meaning the amount of data written to the flash divided by
the amount of data written by the host equals one. However, SSDs
without DuraWrite technology will write many more times to the
flash and can easily have write amplification many times above 1.0.
Excessive write amplification not only reduces performance, but
will prematurely shorten the write lifetime of the flash device. Using
DuraWrite technology with typical data allows write amplification to
In this example the “char” SQL data type is being used. This data type
fixes field width to accommodate the largest permitted value and is
faster to read and update than the “varchar” data type that allows for
variable length strings. The average entry is far below the maximum
limit so the data is highly compressible. In the example above more
than 90% compression3 was possible.
be less than 1! This means that write life will potentially extend longer
than the rated capability of the device if you did not use DuraWrite
technology.
Conclusion
This paper has discussed how DuraWrite technology is designed
to enable the Nytro WarpDrive card to require less flash writes in
Extending Flash Write Life with DuraWrite Technology
In addition to the performance enhancement that comes with
writing less data is the benefit to the flash endurance. When the
flash memory is rewritten less times it will last longer. The extra
most financial or database applications. Less flash writes means that
transactions can happen more quickly and applications accelerate.
Flash write lifetimes extend with DuraWrite technology allowing
many more transactions to occur before the flash needs to be
replaced. DuraWrite technology is a must for enterprise applications.
For more information, visit: www.lsi.com/acceleration
LSI Corporation makes no representations, warranties or guarantees regarding the compatibility or performance of, or
results generated by, specific hardware or software products. The information herein is provided “AS IS” without warranty
of any kind express or implied for use at your sole risk, including without limitation, exclusion of the warranties of
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out of any reliance on or use of this information. Individual results may vary.
1. Results obtained from internal testing at a LSI facility using the VDBench workload generator
(http://vdbench.sourceforge.net/). Individual results may vary.
2. Results obtained from internal testing at a LSI facility using the the gzip UNIX command. Individual results may vary.
3. Results obtained from internal testing at a LSI facility using gzip
(http://gnuwin32.sourceforge.net/packages/gzip.htm). Individual results may vary.
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