Except for very cost sensitive devices, SSDs are the preferred choice for desktops and laptops. However, in large centralized storage servers, enterprise-class SSDs are up to ten times more expensive per capacity than HDDs – but on the other hand HDDs have just 25%-50% of the sequential performance of SSD and are vastly slower when it comes to random access.
In order to provide some fact-based guidance to IT professionals, Toshiba tasked their test and evaluation lab to investigate and provide some results, based upon practical experiments.
The lab installed a total of 60 2TB 7200rpm 12GB/s SAS HDDs (Toshiba MG04SCA20EE) in a RAID10 configuration, giving a net 60TB capacity for the system. For comparison, the lab also built an SSD based system based on eight 1.6TB SATA 6GB/s SSDs in a RAID6 configuration, which cost the same as the HDD solution, but gave a total storage capacity of 9.6TB.
For data archiving purposes, large blocks are written sequentially, so high-speed writing into large low-cost storage capacity is essential. With 1Mbyte data blocks written sequentially, the HDD array achieved 2900MB/s, while the SSD array could only be written at 2500MB/s.
Video streaming/playback reads large blocks in multiple parallel streams. With a workload of 1Mbyte blocks being read sequentially from four jobs, the HDD array will achieve 6400MB/s and the SSD array only 4200MB/s: at the same cost, but only with 1/6 of the net storage capacity. Thus, even with archiving and streaming tasks using HDDs will still be justified for a very long time in the future.
To apply a little more balance to the findings it should be noted that 60 spinning HDDs will consume more power and space than the eight SSDs and, statistically, there is a greater chance of a drive failure within 60 HDDs than eight SSDs. However, the HDD solution provides more than six times the capacity and higher performance for the same expenditure, thanks to the high number of low cost units running in parallel. This is a compelling argument for continued investment in traditional HDD based solutions.
To read about the full test setup and more detailed results, please download Toshiba’s latest white paper here: