Test System and Methodology
The Intel 910 comes in both 400GB and 800GB capacities. The 800GB 910 presents itself to the host operating system as four individual 200GB volumes, while the 400GB version only supplies two of the 200GB volumes. We will be testing both and providing results for the performance of both models.
There is the possibility of using Windows RAID, or a third party program, to aggregate the performance of all of the drives into one large RAID 0 volume. This would be a risky deployment in most applications, but when paired with strong backup schemes in high read and write scenarios, RAID 0 can be a compelling solution. Parity can also be achieved with RAID 5, providing data redundancy at the sacrifice of capacity and write speed.
The configuration that we have tested with provides the best latency results and does a good job of showing the base performance of the 910 itself. This is simply configuring it as four separate LUNs and accessing each individually. This provides low overall latency in conjunction with much lower maximum latencies than RAID 0.
There is an optional Maximum Performance mode that increases the sequential write speed from 1GB/s to 1.5GB/s. This increases the power draw from 25W average to 28W average, with a peak of 38W. We tested with this variable enabled to highlight the maximum performance of the Intel 910. Only Sequential Write speed is affected.
Testing Enterprise Solid State Storage (SSS)
When assessing enterprise flash products the parameters are vastly different than the type of testing conducted upon consumer SSDs and PCIe flash devices. With consumer devices the capacity of the SSD isn't always used at 100% fill and the drive is rarely put under a sufficient enough load to drive it down into its worst performance levels.
Flash is a premium tier in professional environments, costing multitudes of order more money per GB than HDD or tape storage. Every penny that is spent on these high performance EFDs (Enterprise Flash Drives) must be utilized to its fullest potential. This entails using every bit of the storage space available to full capacity and keeping the device under a constant workload for the duration of its lifetime. Unfortunately this type of high-level usage lines up exactly with the worst case scenario for SSDs in terms of both performance and endurance.
All SSDs rely upon spare NAND (Overprovisioning) to complete the majority of their internal functions, keeping the SSD performance at the highest levels possible. Spare area also provides a higher endurance over the lifetime of the SSD as well. Since enterprise SSD devices are typically used to full capacity, there are usually extra levels of overprovisioning to enhance wear levelling, endurance and performance above that of mainstream devices.
Several fundamental aspects of SSD operation are actually hurdles to delivering enterprise class flash devices that yield predictable and sustained performance. Idle time is also used in many consumer SSDs to conduct housekeeping routines, but this is not a reality in an enterprise environment where the SSD will be kept under full load constantly. There are many different approaches that enterprise SSD manufacturers use to mitigate the fact that after prolonged usage the very nature of NAND flash leads to performance degradation.
After prolonged use, all flash-based devices will start to slow down and reach Steady State. Steady State is the "final' level of performance that the SSD will come to when it is placed under continuous load for an extended period of time. This final level of performance has little variability and is far below the performance level that is attained when the SSD is brand new and Fresh Out of Box (F.O.B.).
Finding this level of performance isn't always easy and it is here that we defer to several vital methodologies from SNIA.
Storage Networking Industry Association (SNIA)
SNIA is an industry-accepted group that has defined several parameters crucial for assessing enterprise SSDs. In reality, FOB (Fresh Out of Box) test results are rather useless for determining the performance of these devices, so it is critical that we test under the correct parameters. We have adopted several of SNIAs central approaches into our testing program here at TweakTown, which will ensure that we observe the devices under the appropriate Steady State conditions.
Steady State is attained by applying a heavy-write workload over the full span of the SSD over an extended period of time. Steady State can also vary depending upon the type of workload that is placed upon the SSD, so using the correct type of loading is also important.
The three steps of the process are to apply Workload Independent Preconditioning (WIP), Workload Based Preconditioning (WBP) and then verification of Steady State Convergence.
During the WBP we log the performance data to ensure that Steady State has been attained - the slope is less that 10% min/max. Once we have confirmed Steady State Convergence is within the desirable test range on the graph above, we begin data logging.