RAID considerations In this current (at the time of writing) release of Storwize code (version 7.7.0/7.6.1.4), RI SSDs are assigned a tech_type of sas_hdd at 10,000 revolutions per minute (RPM). Due to this fact and the limitations on the write capability of these SSDs, the following leading practices apply when you create Redundant Array of Independent Disks (RAID) configurations: It is required that Read Intensive SSDs RAID and managed disk (MDisk) pools are created manually. If you are configuring a new system, create RI SSD RAIDs and pools before you configure other drives (other SSDs, Enterprise and Nearline serial-attached SCSI (SAS) drives). If you are adding RI SSDs into an existing system, create RAID and storage pools manually. Do not mix RI SSD and any other drive type in the same pool. Given that RI SSDs are assigned a tech_type of sas_hdd and 10,000 RPM, it is possible that automatic configuration tools might mix these SSDs with other 10,000 RPM hard disk drives (HDDs). This can affect RI SSD array performance. It is strongly advised that automatic storage configuration tools are not used for these SSDs. It is imperative that enough spare RI SSDs are made available for RI SSD arrays. If a drive in an RI SSD array fails and a matching RI SSD is not available as a spare, the system picks up a HDD of matching or higher capacity and incorporates it into the RI SSD array. This impairs the performance of the entire RI SSD array. It is essential that sufficient spare RI SSDs are available to maintain exclusivity of RI SSD arrays.