This section describes how a combination of the IBM FlashSystem and another disk storage  can add redundancy and allow the use of software functionalities in other storage to provide  outstanding performance for the applications with standard I/O behavior. The examples that are included in this section show the possible combinations in a  preferred  read  implementation and how they can be expanded to other applications. The preferred read solution approach allows the application to use the lowest latency for  reads, or read at the speed of the IBM FlashSystem 900, because the main goal of this  solution is to send all read requests to the IBM FlashSystem 900. Preferred read presumes a  write mirroring  relationship in which the I/O is written to two or  more storage subsystems. Also, all read I/O requests are served from the IBM FlashSystem  900.  A high-level example of how preferred read works is shown in Figure 11-2. The preferred read solution adds another level of protection, as shown in Figure 11-3 on  page 403. For example, if a power failure occurs in a disaster situation on the IBM  FlashSystem 900 and it becomes unavailable, the application continues to access the data  without interruption and without data loss because, in preferred read, all the data is mirrored  (to both storage products). Figure 11-2 Preferred read overview 402  Implementing IBM FlashSystem 900 Model AE3