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Review: Sandisk Optimus ECO SAS 400GB Enterprise |
Welcome to Myce’s review of the Optimus ECO SAS 400GB
Enterprise SSD. The last time we reviewed an Optimus was before Smart Storage
Systems was acquired by Sandisk and it proved to be a truly outstanding drive.
So, we were excited to receive the new Optimus ECO in the SanDisk livery and as
you will see it does not disappoint.
Market Positioning and Specification
Market Positioning
This is how Sandisk positions the Optimus ECO –
Sandisk sees their Guardian technology as a key competitive
differentiator -
Specification
Here is Sandisk’s specification for the Optimus ECO –
Product Image
Here is a picture of the Optimus ECO we tested –
The Optimus ECO has a dual/wide port capability - this
allows bandwidth to be aggregated across its two SAS links, which permits data
to be streamed in both directions, thereby providing improved performance.
In addition to the single port results for our testing we
present the results for wide port testing in the SNIA Throughput test (where
the wide port capability has its most significant impact) and in the
Oakgate/Myce Performance Characterisation tests.
Now let's head to the next page, to look at Myce’s
Enterprise Testing Methodology.....
NEW PAGE NEW PAGE NEW PAGE NEW PAGE
Please click
here
to view or download a detailed introduction to Myce’s Enterprise Class Solid
State Storage (‘SSS’) Testing Methodology as a PDF.
Put briefly:
All testing is performed on an OakGate Technology test unit
We perform two sets of Performance Tests:
- A full set of the mandatory Storage Network Industry
Association’s (‘SNIA’) tests as specified in their Solid State Storage
Performance Test Specification Enterprise V1.0 – SNIA
SSS PTS Version 1.0. - A set of tests, known as the ‘Myce/OakGate Full
Characterisation Test Set’, that provides readers with a fuller
characterisation of the solution.
We also review other important factors such as Power
Consumption, Data Reliability and Failover features.
A word about SNIA testing – before striking a partnership
with OakGate Technology I spent some time researching how I might implement
SNIA testing using freely available tools such as IOMeter and FIO. I arrived
at the conclusion that whilst it was theoretically possible it was
impractical. The reason for this is as without the automation offered by a
test bench, such as the OakGate Unit, the only way to meet the SSS PTS
requirements is to run the maximum number of test cycles and then to manually
look back at the results to determine when/if steady state has been achieved in
the workload specific test cycle, and then harvest the data from the qualifying
Measurement Window. This means that the test runs would always take a maximum
elapsed time, and there would be a great deal of human effort required to
review, gather, and report upon the data. I empathise with, acknowledge, and
respect the efforts of other reviewers who endeavour to meet the SNIA’s
principles in their testing - I am privileged and thankful to be able to use a
superb test bench which automates the whole process and allows me to meet the
SNIA’s specification in full.
Before we move on, let’s remind ourselves of some basics –
When reviewing the performance of an SSS solution there are
three basic metrics that we look at:
1. IOPS – the number of
Input/Output Operations per Second
2. Bandwidth – the number of
bytes transferred per second (usually measured in Megabytes per second, ‘MB/s’)
3. Latency – the amount of time
each IO request will take to complete (usually, in the context of SSS
solutions, measured in Microseconds, which are millionths of a second).
It is true to say that IOPS and Bandwidth had all been
growing rapidly before the advent of SSS solutions, but Latency can only be significantly
decreased by eliminating mechanical devices, and thus Latency is the single
most important aspect that SSS solutions deliver to enhance performance.
Latency in a technical environment is synonymous with delay.
In the context of an SSS solution it is the amount of time between an IO
request being made, and when the request is serviced.
Bandwidth, also commonly referred to as ‘Throughput’, is the
amount of data that can be transferred from a storage device to a host, in a
given amount of time. In the context of SSS solutions it is typically measured
in Megabytes per second (MB/s).
A great enterprise SSS solution
offers an effective balance of all three metrics. High IOPS and Bandwidth is
simply not enough if Latency (the delay in an IO operation) is too high. As we
will see in the test results presented below, as Latency increases IOPS will
inevitably decrease.
Queue Depth is the average amount
of IO requests outstanding. If you are running an application and the Average
Queue Depth is one or higher and CPU utilisation is low, then the application’s
performance is most probably suffering from a ‘Storage Bottleneck’.
Another important factor to
remember is that SSS performance is influenced by previous workloads, not just
the current workload, and especially by what has previously been written to the
drive. As specified in the SNIA SSS PTS the goal of all good Enterprise level
testing is to provide consistent circumstances, so that results can be compared
fairly across different SSS solutions – it is for this reason that all of our
tests start with a purge of the drive, so that it starts in a ‘Fresh Out of the
Box’ (FOB) state. Most tests then have a pre-conditioning phase where the
drive is put into a ‘Steady State’ before the test phase begins. Put briefly, a
‘Steady State’ is achieved when the performance of the drive no longer varies
over time and settles into a consistent level of performance for the workload
in hand. You can find a detailed explanation of ‘Steady State’ and how it is
determined in the SNIA tests in our Enterprise Testing Methodology paper, which
can be viewed or downloaded as a PDF by clicking here.
For interest, here are some
generally accepted assumptions that differentiate the use and therefore the
approach to testing Enterprise/Server and Consumer/Client SSS solutions:
Enterprise/Server SSS
assumptions:
- The drive is always full
- The drive is being accessed 100% of the time (i.e. the
drive gets no idle time) - Failure is catastrophic for many users
- The Enterprise market chooses SSS solutions based on their
performance in steady state, and that steady state, full, and worst case
are not the same thing
Consumer/Client SSS
assumptions:
- The drive typically has less than 50% of its user space
occupied - The drive is accessed around 8 hours per day, 5 days per
week, and typically data is written far less frequently - Failure is catastrophic for a single user
- The consumer/client market generally chooses SSS solutions
based on their performance in the FOB state
Esther
Spanjer, Director, SSD Technical Marketing at Smart Storage Systems, said, 'I
am happy to commend Myce for their high level of professionalism and
cooperation during the review process', Ms. Spanjer added, 'I wish them every
success in their partnership with OakGate Technology and their initiative to
provide authoritative performance reviews for the Enterprise Solid State
Storage market'
Now let's head to the next page, to look at the results
of our SNIA IOPS (Input/Output Operations per Second) Test.....
IOPS performance will typically
vary greatly depending on the nature of the IO traffic, including the mixture
of Read and Write operations, and the mixture of Block Sizes (the size of the
IO operation’s data packet, also referred to as IO Size). This test is designed
to benchmark the IOPS performance profile for random IO operations for 56
different combinations of Read/Write mix % and Block Sizes when in a Steady
State, which are of interest to most users.
All of the SNIA’s test
specifications define a ‘required’ set of parameters that must be run for the
test and then allow the operator to elect to run additional tests with
different parameters of their choice. It is the mandatory test with the
required parameters that we run. Note that all of the mandatory tests must be
conducted with fully random data
As previously mentioned, a key
principle of SNIA testing is to provide a consistent basis for comparing
different solutions from different manufacturers.
Here are the results -
You can see here a visual confirmation that Steady State
Convergence was determined at the end of Round 5.
Here is a 3D and tabular presentation of the results. Users
can simply refer to the grid to obtain the R/W mix and Block Size value of
interest. For example, Online Transaction Processing applications
typically run at a Block Size of 8K and a Read/Write Mix of 65/35, and users
can quickly understand how the device might perform under Steady State for
these access characteristics.
You can see that the 4K 100% Read IOPS result is 96,440 and
that the 4K 100% Write IOPS result is 36,617 which both happily exceed Sandisk’s
specification.
Product Comparison
For interest we present a comparison of the 4K 100% Writes
and Reads results with those of the other Enterprise SSDs we have tested -
You can see that the Optimus ECO has excellent write performance,
lying second to only the original Optimus.
Now let's head to the next page, where we look at the
results of the SNIA Write Saturation Test.....
The objective of this test is
to observe the time evolution of the drive’s performance, as a function of
time, from a ‘factory fresh’, ‘fresh out of the box’ (‘FOB’) state. When a
drive is in a FOB state (e.g. after it has been purged by, for example by a
SATA Secure Erase or SCSI Format), we can expect an initial period of time when
writes can easily be accommodated by clean/empty blocks, but once all of the clean
blocks have been written to once and the drive’s controller must first clean
blocks (with erase write operations) before it can write new data, then we can
expect a slow down. The slow-down is usually quite dramatic and is commonly
referred to as the ‘write cliff’.
The Write Saturation Test is
easy to run as it requires no steady state determination – it can be easily run
in freely available software, such as IOMeter.
Here are the results -
You can see here a slight drop in Write IOPS performance as
the Optimus ECO reaches a Steady State. The fall, at around Round 47, occurs
when all of the available NAND has been written to once and the drive must
clean blocks on the fly, in preparation for accommodating further writes – this
is commonly referred to as the ‘Write Cliff’ (though for the Optimus ECO, just
as it was for the original Optimus, it is more of a small ‘bank’ than a ‘cliff’).
The Optimus ECO shows excellent consistency.
Note that the test was halted, as specified in the SNIA SSS
PTS, when 4 x the User Capacity had been written to the drive. You can see that
the Optimus ECO is settling into a steady state at around the 38,000 IOPS level,
which is excellent.
You can also see that the latency graph line is a mirror
image of the IOPS graph line.
Now let's head to the next page, to look at the SNIA
Throughput Test.....
The test is designed to measure the sequential Read and
Write IO performance for two Block Sizes, when under Steady State conditions.
One can easily compare the results produced by this test with box-top numbers,
which are usually stated as “Up to xxx MB/S”.
Here are the results -
For single port -
You can see here that Steady State was achieved for both
Write IO sizes by the end of Round 5.
For dual/wide port -
-
For single port -
You can see here that Steady State for both Read IO sizes
was achieved by the end of Round 6.
For dual/wide port –
Here are the average values recorded in the measurement
window, for single port –
…and dual/wide port -
You can see that the results for dual port testing are
significantly better than those for single port but having said this the
results for single port are excellent (as can be seen in the product comparison
tables below). We test for the maximum throughput in dual/wide port mode in
the Myce Reads and Writes tests later in this review.
Product Comparison
For interest we present a comparison of the 1024K sequential
reads and writes (single port) performance in comparison with those of the
other Enterprise SSDs we have tested -
Now let's head to the next page, to look at the results
of the SNIA Latency Test.....
The Latency Test measures average and maximum response times
using random IOs at specified Block Sizes and Read/Write mixes, taken under
steady state conditions. The test runs at a Queue Depth of 1 (1 outstanding
IO), thus the results give the baseline response time for a single IO request.
The test also reports maximum latency values, which can be
helpful to see if there might be processes within the drive that may cause max
Latency values to become larger.
Here are the results -
You can see here that Steady State Convergence was achieved
at the end of Round 5.
These are the Average and Maximum Latency Values observed in
the Measurement Window (measured in Milliseconds).
Here is a 3D graph showing, at a glance, the Maximum Latency
values for each combination of Read/Write Mix and IO Size.
Here is a 3D graph showing, at a glance, the Average Latency
values for each combination of Read/Write Mix and IO Size. These are very good
Latency results.
Product Comparison
For interest we present a comparison of the 4K 65% Reads 35%
Writes latency results in comparison with those of the other Enterprise SSDs we
have tested -
Now let's head to the next page, to look at the results
for the Myce/OakGate 4K Read and Write Latency Tests......
These tests steadily increase the random 4K IO demand in
terms of IOPS, and report the drive's response in terms of Average IOPS, Average
Latency and Maximum Latency. It is designed to show a drive’s maximum IOPS
capability and report the all important Latency numbers for each level of IOPS
demanded. The Maximum latency numbers give us an insight into the occurrence
of Latency peaks that could cause an unexpected response from time to time.
Here are the results –
Firstly, here is a graph showing the result for the
Pre-Conditioning –
For single port -
For dual/wide port -
4K Latency Read Test
For single port -
You can see that the drive can no longer meet the increase
in IOPS demand at 80,000 IOPS, which, in the context of this test, is falling
slightly short of Sandisk’s specification of 90,000. I have realised that
there is an error in my test script that is causing the response to the IOPS
demand to be capped at 80,000; so please disregard this result
For dual/wide port –
For single port -
You can see a gradual increase in read latency up to the
maximum IOPS mark. The Read Latency results are excellent.
For dual/wide port -
For single port –
These are excellent results for maximum latency values,
which speaks volumes for the consistency of the Optimus ECO.
For dual/wide port -
These are excellent results for maximum latency values,
which speaks volumes for the consistency of the Optimus ECO.
Let’s have a look at the distribution of the Latency results
(for single port) at the 65,000 IOPS level –
As this is the first time in this review, that we are
looking at a High Resolution Latency Histogram, here’s an explanation – The X
axis to the left is the count of the IOs in the observation period (in a Round)
that had a Latency of the value along the Y axis (please note that the X axis
is logarithmic to allow the low order counts of the huge number of IOs that
have been measured to be visible); the Y axis is the Latency value measured in
Microseconds; The X axis to the right is the % of the Total IOs observed that
have a Latency <= to a given Latency value; the rate of getting to 100% is
highlighted by the red graph line.
You can see that 99.9% of the Latency values are <= 290
Microseconds and there are relatively few outliers.
4K Latency Write Test
For single port -
You can see here that the Optimus ECO starts failing to meet
the increase in IOPS demand at around 37,500. This is an excellent result,
which exceeds Sandisk’s specification.
For dual/wide port -
For single port -
Here we can see that Average Write Latency stays below 200
Microseconds until a demand of 36,000 IOPS.
For dual/wide port -
For single port -
The maximum write latency results are more ‘peaky’ than
those for reads, but this is typical.
For dual/wide port -
Now let’s have a look at the distribution of the Latency
Values (for single port testing) at the 36,000 IOPS Mark –
You can see that 95% of the Latency Values are <= 490
microseconds. This is an excellent result.
Now let's head to the next page, to look at the results
for the Myce/Oakgate Reads and Writes Tests.....
Myce/OakGate Reads and Writes Tests
The tests are designed to show the Random and Sequential,
Read and Write, performance metrics for different combinations of Queue Depth
and IO size.
Here are the results -
Random Reads
For single port -
For dual/wide port -
For single port -
For dual/wide port -
For single port -
For dual/wide port -
Random Writes
For single port -
Here you can see a distinctive and healthy IOPS peak for the
4K IO Size.
For dual/wide port -
For single port -
For dual/wide port -
For single port -
For dual/wide port –
Sequential Reads
For single port -
For dual/wide port –
For single port -
For dual/wide port –
For single port -
For dual/wide port -
Maximum Throughput/Bandwidth
I experimented with the OakGate test unit’s IO Exerciser to
see what conditions would lead to the highest Sequential Read throughput in
dual/wide port testing. I found that performing 512K Sequential Writes
followed by 512K Sequential Reads produced the highest performance as follows –
You can see that this gives an average Sequential Read
throughput of 1,083.91 – over 1 GB/s, very impressive!
I acknowledge that these are ideal, laboratory conditions
but nevertheless it is a very impressive result. The only other times I have
seen a single drive read at over 1 GB/s was with the original Smart Optimus (when
running in wide port mode) and with the Toshiba PX02SMF020 (which is a 12GB/s
drive).
Sequential Writes
For single port -
For dual/wide port –
For single port -
For dual/wide port -
For single port -
For dual/wide port -
Now let's head to the next page, to look at the results
for the Myce/Oakgate 4K Mixed Reads/Writes Tests.....
This test is designed to show the performance metrics for
different combinations of Queue Depth and Read/Write mix (the % of Reads and
the % of Writes making up the IO traffic)
4K Mixed R/W Test
For single port -
For dual/wide port -
You can see that there is no dramatic decrease in Read IOPS
as a small % of writes enters the mix.
For single port -
For dual/wide port –
For single port -
For dual/wide port -
For single port -
For dual/wide port –
For single port -
For dual/wide port –
For single port -
For dual/wide port -
For
single port -
For dual/wide port -
For single port -
For dual/wide port –
For single port-
For dual/wide port -
Now let's head to the next page, to look at the results
of the Myce/OakGate Entropy Tests.....
These tests are designed to show performance metrics for
different combinations of Queue Depth and Entropy % (Entropy % is the degree to
which the data that is random and therefore incompressible). Testing with
different Entropy % levels has become important with the advent of controllers,
such as those from LSI Sandforce, that compress data before writing it to NAND.
Controllers that compress data can be expected to perform better with highly
compressible data (i.e. data with low Entropy).
The first test performs 5 minutes of Random 4K writes for each
combination of Queue Depth and Entropy %.
The second test does the same thing for a mixture of Read
and Write traffic (70% Reads, 30% Writes).
4K Entropy Write Test
You can see there is little or no variance in performance to
be found in any of the Entropy tests, as the degree of random data increases
(and this comment applies to all of the test results for the Myce/OakGate
Entropy Tests). We can therefore conclude that the Optimus ECO does not
compress data.
4K Entropy 70%_Reads_30%_Writes Test
As we saw no evidence of compression in the 4K Entropy Write
Test we skip the presentation of the 70/30 entropy results.
Now let's head to the next page, to look at Power
Consumption and Data Reliability.....
Power Consumption
I believe most people know that data centres are already one
of the major consumers of electricity in the industrialised world; indeed it is
estimated that currently 2% of all electricity consumption goes into IT
applications. According to the European Union the energy consumption of data
centres was 46 Terawatt hours in 2006 and is set to rise to 93 TW hrs by 2020. This
is equivalent to one hundred million 100W light bulbs burning 24 hours a day,
365 days a year.
Typically 40% of the power consumed by data centres is for
the IT load and 35% is for cooling the system. Generally speaking, if a drive
consumes more power it will produce more heat – so power consumption is indeed
a double edged sword. It is no surprise then that a significant proportion of
a data centre’s power consumption goes on servers. I understand cloud based
applications, such as Facebook, are the primary cause of the growth in servers
and the demand for storage space.
If you are a Facebook user, like me and the Reynolds sibs, and
you reside in Europe – this is most probably where your data is click here. Some
interesting Facebook statistics – Facebook has more than 1 Billion monthly
active users, it generates 1 Trillion page views per month and more than 219
Billion photos have been uploaded since launch – amazing! Here is an
interesting video showing the remarkable scale of Facebook’s largest North
American data centre click
here.
My thanks to Anna of Intel for pointing me to the following
Info-graphs -
The following graph uses the typical Power Consumption, when
active, as published in the respective manufacturer’s specification. The value
for the Kingston E100 is calculated as the average of 1.2W (TYP) Read and 2.7W
(TYP) Write.
The Optimus ECO’s Power Consumption is specified by Sandisk
to be 7 Watts, which is good for an SAS drive.
Data Reliability
The 'Unrecoverable Bit Error
Rate' (UBER),as defined by JEDEC, the global leader in developing open
standards for the microelectronic industry, is a metric for data corruption
rate equal to the number of data errors per bit read after applying any
specified error correction method. UBER = number of data errors / number of
bits read. JDEC specifies that the maximum error rate allowable for an
Enterprise level SSS solution is one error in every 10^16 bits read.
Sandisk specifies an UBER of 1 in 10^17 bits read
for the Optimus ECO.
The Optimus ECO has a 5 year warranty and is warranted for 3
Drive Writes Per Day (DWPD) for random workloads.
The Optimus ECO includes Sandisk’s Guardian Technology and
thus has a comprehensive set of Enterprise features, which includes power
failure support.
Now let's head to the next page, to look at the
Conclusions of this review.....
The Smart Optimus ECO is another excellent drive following
in the Optimus line.
For its target market of mixed use and read intensive
applications it offers an excellent balance of consistent performance together
with endurance, data reliability, and data integrity features.
Dual/wide port Sequential Read Throughput of greater than 1
Gigabyte per second is a ‘wow’ factor.
I found the Optimus ECO 400GB available for a price of
£549.99, which is a good price for a fully featured SAS drive.
I am pleased to award the Optimus ECO our rating of 'Excellent'.
