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 significant drop in Write IOPS
performance as the Intel P3700 reaches a Steady State. The fall, that begins at
around Round 23, 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’.
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 Intel P3700 is settling into a steady
state at just over 150,000 IOPS, which is stunning.
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