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Serial Cables 24-bay 12Gbps SAS Enterprise JBOD Enclosure Review

By: Paul Alcorn | RAID/HBA in IT/Datacenter | Posted: Feb 20, 2015 3:10 pm
TweakTown Rating: 91%Manufacturer: Serial Cables

4k Random Read/Write




We precondition the array of eight HGST SSD800MH SSDs for 9,000 seconds, or two and a half hours, receiving performance reports every second. We plot this data to illustrate the drives' descent into steady state.


This dual-axis chart consists of 18,000 data points, with the IOPS on the left, and the latency on the right. The red dots signify IOPS, and the grey dots are latency measurements during the test. We place latency data in a logarithmic scale to bring it into comparison range. The lines through the data scatter are the average during the test. This type of testing presents standard deviation and maximum/minimum I/O in a visual manner.


Note that the IOPS and latency figures are nearly mirror images of each other. This illustrates high-granularity testing can give our readers a good feel for latency distribution by viewing IOPS at one-second intervals. This should be in mind when viewing our test results below. This downward slope of performance only occurs during the first few hours of use, and we present precondition results only to confirm steady state convergence.




Each level tested includes 300 data points (five minutes of one second reports) to illustrate performance variability. The line for each OIO depth represents the average speed reported during the five-minute interval. We include a smaller embedded chart that lists performance at the highest load for easy interpretation.


4k random speed measurements are an important metric when comparing drive performance, as the hardest type of file access for any storage solution to master is small-file random. 4k random performance is a heavily marketed figure, and is one of the most sought-after performance specifications.


In our testing, we are searching for any performance variation between two arrays; one array is directly attached via cabling to the RAID controller, and the other array is connected via the Serial Cables enclosure. If the Serial Cables enclosure provides little to no effect to the native performance of the 12Gb/s SAS SSDs, the results will be somewhat repetitive. This holds true as we start our testing with both arrays reaching 515,000 IOPS, with very little performance variation between direct cabling and the Serial Cables enclosure. We do note some variability at 64 OIO, but this is likely due to internal drive management.






Our Latency v IOPS charts compare the amount of performance attained from each solution at specific latency measurements. Many applications have specific latency requirements. These charts present relevant metrics in an easy-to-read manner for readers who are familiar with their application requirements.


Both methods of connection, cable and JBOD, exhibit such small latency variation that the lines overlap perfectly in our IOPS v Latency test.




Garbage collection routines are more pronounced in heavy write workloads, leading to performance variability.


4k random write workloads are more demanding for the SSDs, and here we can see the enclosure performing admirably with no impact to the base performance of the SSDs.






The 4k random write results mirror the results we received with random read testing, and the line displaying the JBOD's performance overlaps the DAS connection perfectly.






Our write percentage testing illustrates the varying performance of each solution with mixed workloads. The 100% column to the right is a pure 4k write workload, and 0% represents a pure 4k read workload.


The JBOD remains impressively consistent, even with mixed workloads compared to a direct-cabled connection. Both latency and IOPS performance are strikingly similar.

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