In September 2017 IBM introduced a new class of Flash for the DS8880 with a new 3.8TB High Capacity Flash
drive. Earlier this year we continued to increase the High Capacity Flash sizes with the introduction of the 7.6TB High Capacity Flash
drive, and now on the 20th November 2018 we have introduced a still larger 15.36TB drive
In January I provided some thoughts
on how these High Capacity Flash drives could be used either on their own or on combination with High Performance Flash drives to improve storage density and reduce costs while still providing excellent performance for many workloads.
Not all Flash drives are created equal from a performance perspective, and as well a being larger the 7.6TB and 15.36TB drives have somewhat different performance characteristics from the previous capacities of High Performance and High Capacity Flash. The graph below shows the performance characteristics of a single array of different sizes of High Capacity Flash drives contrasted with the 3.2TB High Performance Flash drives.
This shows that the read performance of the different drives is roughly similar, while the sequential and random write performance decreases with the larger drives.
Continuing the changes introduced with the 3.8TB High Capacity Flash, Easy Tier can be used to manage different combinations of Flash types and sizes. The 7.6TB and 15.3TB drives are classified as a third Flash tier below the 3.8TB and High Performance Flash drives.
Given the range of options available in terms of drive capacities and the possibility to use Easy Tier to combine different types of drives it is helpful to consider what a sensible starting point might be when configuring a DS8880. This is shown in the following table
As always it is important to validate performance requirements with Disk Magic, but experience has shown that the majority of workloads will fit within these configurations.