performs random 4K writes.
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 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 steep fall followed by a gradual drop in
Write IOPS performance as the Seagate 1200 reaches a Steady State. The fall that
begins at around Round 17 is 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 Seagate 1200 is settling towards a steady state at around the 42,000 IOPS
level, which is excellent.
You can also
see that the latency graph line is a mirror image of the IOPS graph line.
head to the next page, to look at the SNIA Throughput Test…..