Seagate 1200 400GB SAS Enterprise SSD Review

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 –

Seagate 1200 400GB SAS Enterprise SSD Review

 

Seagate 1200 400GB SAS Enterprise SSD Review

 

Power Testing

We present
our standard set of power consumption tests.

SNIA Write
Saturation

 

Seagate 1200 400GB SAS Enterprise SSD Review

This test allows us to observe the power consumption
characteristics as the drive passes from a fresh ‘out of the box’ state to one
where blocks must first be cleaned before they can be written to.  It also
allows us to form a view on the amount of power that is being consumed by the
cleaning of the blocks (for 4K random writes). We can see a slight increase in
power consumption after hitting the write cliff at round 17, but roughly
speaking, by round 105 we can see that 6,000mW is required to sustain around
42,000 IOPS whereas before the write cliff, the same level of power was
sustaining nearly 110,000 IOPS. Thus we can deduce that roughly 68,000/110,000
of the 6,000mW (i.e. roughly 6/10 of the power) is consumed by housekeeping. 


4K Latency
Test – Reads

Seagate 1200 400GB SAS Enterprise SSD Review

This test allows us to observe how power consumption
characteristics vary as the demand for random 4K reads (in terms of IOPS) is
increased.  You can see that the demand for power increases gradually and in a
linear fashion.  We could use these two lines to calculate the sweetspot where
one would consume the least power per IO, however as the rate of increase in
power consumption is not as steep as the increase in IOPS we know intuitively
that the best power consumption to IO ratio is at the maximum IOPS level.


4K Latency
– Writes

Seagate 1200 400GB SAS Enterprise SSD Review

 

This test allows us to observe how power consumption
characteristics vary as the demand for random 4K writes (in terms of IOPS) is
increased.  You can see that the demand for power increases gradually and in a
linear fashion.  We could use these two lines to calculate the sweetspot where
one would consume the least power per IO.  However, as the rate of increase in
power consumption is not as steep as the increase in IOPS we know intuitively
that the best power consumption to IO ratio is at the maximum IOPS level.


4K Mixed
Reads/Writes

Seagate 1200 400GB SAS Enterprise SSD Review

 

This test allows us to see how power consumption
characteristics vary when performing 4K random reads and writes with different
combinations of read/write % and queue depth.  As would be expected, you can
see that as one increases the % of writes the power consumption increases.

We have then
taken the data to calculate the IOPS per mW for each combination, as follows –

Seagate 1200 400GB SAS Enterprise SSD Review

The IOPS per mW results can then be compared to those for
the Toshiba THNSN960PCSZ (the drive with the best power consumption results,
that has thus far been subjected to our Enterprise Power Tests).

Seagate 1200 400GB SAS Enterprise SSD Review

You can see
that the Toshiba is significantly more efficient particularly for read
activity. However, we must keep in mind that SAS drives are typically more
power hungry than SATA drives.


Sequential
Writes

(I apologise
for not presenting the results for Sequential Reads on this occasion)

Seagate 1200 400GB SAS Enterprise SSD Review

This test allows us to see how power consumption
characteristics vary when sequential writes with different combinations of IO
Size and queue depth.  As might be expected, the power consumption increases as
the MB/s increases.

 

We have then used
this data to calculate the MB/s per mW as follows –

Seagate 1200 400GB SAS Enterprise SSD Review

The MB/s per
mW results can then be compared to those for the Toshiba THNSN960PCSZ (the
drive with the best power consumption results, that has thus far been subjected
to our Enterprise Power Tests).

Seagate 1200 400GB SAS Enterprise SSD Review

Again, you can see that the Toshiba is significantly more power
efficient.


Power Up
to Idle

Seagate 1200 400GB SAS Enterprise SSD Review

This test
allows us to see the shape of the power demand as a drive is powered up. It
also allows us to see the peak level of current demanded to kick the drive into
life.

As you can
see power is drawn from both the 12v and 5v rails.

Seagate specifies that the ‘Max Start Current’ required is
0.7A from the 5v rail and 0.4A from the 12v rail.  Well if you look at the
Current (mA) Graph above you can see a very short peak on the 5v current (at
around 400mS) that has exceeded 1000mA (1A) and a more sustained peak on the 12v
current (between 2,200 and 2,800 mS) that edges above 400mA (0.4A).  So our incredibly
accurate Quarch equipment finds that Seagate’s specification for the Seagate
1200’s Max Start currents are a bit ambitious.  

Seagate 1200 400GB SAS Enterprise SSD Review

Here is a
closer look at the first 150 mS.  You can see that the drive springs into life
when the supply has reached around 3,900mV on the 5v rail.


Idle

Seagate 1200 400GB SAS Enterprise SSD Review

This test
allows us to view the power consumption characteristics when a drive is idling
(powered up but with no IO activity).

Seagate 1200 400GB SAS Enterprise SSD Review

Here is a
picture of the raw data values that were recorded.

Seagate 1200 400GB SAS Enterprise SSD Review

Here are the
statistics calculated for the recording.

The average
power used when idling was 2100mW from the 5v rail and 881mW from the 12v rail
giving a total of 2981mW (2.981W), which can be compared to Seagate’s
specification of 2.72W.


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.

Seagate specifies an UBER of 1 in 10^16 bits read
for the Seagate 1200.

Seagate 1200 400GB SAS Enterprise SSD Review

The Seagate
1200 400GB is warranted to support up to 7300 Terabytes of writes over 5 years
(which equates to 10 Drive Writes per Day).

The Seagate
1200 includes sophisticated power failure support and end-to-end data
protection.

The Seagate
1200 benefits from the inherent failover support provided by SAS drives.

 

Now let’s
head to the next page, to look at the Conclusions of this review…..