So, you can speed up an application by accelerating the read I/Os. Implementing preferred  read with the IBM FlashSystem provides an easy way to deploy the IBM FlashSystem in an  existing environment. The data is secured by writing it to two different storage systems. Data  is read at IBM FlashSystem speed because it is always read from the IBM FlashSystem. This  implementation does not change the existing infrastructure concepts, for example, data  security, replication, backup, and DR. On AIX, preferred read is implemented by the AIX LVM. The following steps show you how to  create a preferred read configuration with the IBM FlashSystem. The steps assume that the  AIX server is cabled and zoned correctly. You may also set the scheduling policy for reads and writes to the storage systems. If you use  mirrored logical volumes, the following scheduling policies for writing to disk can be set for a  logical volume with multiple copies: 1. Create a file system on a HDD. 2. Add the IBM FlashSystem as a mirrored copy to this file system. 3. Set the correct read and write policy. 4. Set the preferred read to the IBM FlashSystem. GLYPH<SM590000> Write operations are done in parallel to all copies of the mirror. GLYPH<SM590000> Read operations are always performed on the primary copy of the  devices in the mirror set. Sequential scheduling policy Parallel scheduling policy Parallel write with sequential read scheduling policy Parallel write with round-robin read scheduling policy Performs writes to multiple copies or mirrors in order. The multiple  physical partitions (PPs) representing the mirrored copies of a single  LPAR are designated primary, secondary, and tertiary. In sequential  scheduling, the PPs are written to in sequence. The system waits for  the write operation for one PP to complete before starting the write  operation for the next one. When all write operations are complete for  all mirrors, the write operation is complete. Simultaneously starts the write operation for all the PPs in an LPAR.  When the write operation to the PP that takes the longest to complete  finishes, the write operation is complete. Specifying mirrored logical  volumes with a parallel scheduling policy might improve I/O  read-operation performance because multiple copies allow the system  to direct the read operation to the least busy disk for this logical volume. Simultaneously starts the write operation for all the PPs in an LPAR.  The primary copy of the read is always read first. If that read operation  is unsuccessful, the next copy is read. During the read retry operation  on the next copy, the failed primary copy is corrected by the LVM with a  hardware relocation, which patches the bad block for future access.  Simultaneously starts the write operation for all the PPs in an LPAR.  Reads are switched back and forth among the mirrored copies. You must set the policy to parallel write with sequential read to get the  preferred read performance of the IBM FlashSystem. With this option,  you get these functions: Note:  Downtime for the file system is required when you change the LVM scheduler policy. 42  IBM AIX Enhancements and Modernization