The WD Surveillance Benchmark also displays histograms of the read and write completion times. When you start to stress the drives, writes take priority over the read operations, and their completion times start to drift upwards. This is what you want to see; if you have to drop data, you'd rather lose information played back than the stream you're trying to record. For all drives, write completions were always less than 20 ms.
In the graph above, we are looking solely at read completions times.
In the first test case, all products perform well. Everything except the WD Red has 50% of its read commands complete in less than 20 ms. Moving to the more demanding test cases proves to be problematic for the non-enterprise drives.
The Seagate Surveillance HDD has slightly better read distributions than WD's Purple, and in the next section, we'll see how the actual distribution looks for both disks.
Looking at the enterprise drives, you can see that they are better equipped to handle more demanding workloads. In fact, the Seagate Savvio 15K.3 just plows through the tests. Even though the idle time for the 32/720p/30 FPS lands at 9%, almost 100% of the writes and reads are still under 20 ms.
- Introducing Surveillance-Specific Hard Drives
- Western Digital Purple
- Seagate Surveillance HDD
- How We Test Surveillence HDDs
- Results: Transfer Rate And Access Time
- Results: WD Surveillance Benchmark, Idle Time
- Results: WD Surveillance Benchmark, Read Completion
- Results: WD Surveillance Benchmark, Distributions
- High-Capacity Hard Drives Built With Surveillance In Mind