The wizard guides you through the steps for moving a volume to another I/O group, including  any changes to hosts that are required. For more information, click  Need Help  in the  associated management GUI windows. Additional information regarding volume migrations between I/O groups can be found at IBM  Knowledge Center: IBM FlashSystem 9100 Knowledge Center - Managing Volumes Host operating system and host bus adapter software must have a way to fairly prioritize I/O  to the storage. The host bus might run faster than the I/O bus or external storage. Therefore,  you must have a way to queue I/O to the devices. Each operating system and host adapter  have unique methods to control the I/O queue. The unique method to control I/O queue can  be host adapter-based or memory and thread resources-based, or based on the number of  commands that are outstanding for a device.  You have several configuration parameters available to control the I/O queue for your  configuration. The storage adapters (volumes on IBM FlashSystem 9100) have host adapter  parameters and queue depth parameters. Algorithms are also available within multipathing  software, such as the  qdepth_enable  attribute.  Queue depth  is used to control the number of concurrent operations that occur on different  storage resources. Queue depth is the number of I/O operations that can be run in parallel on  a device.  Guidance about limiting queue depths in large SANs as described in previous IBM  documentation was replaced with a calculation for homogeneous and nonhomogeneous FC,  iSCSI and iSER hosts. This calculation is for an overall queue depth per I/O group. You can  use this number to reduce queue depths that are lower than the recommendations or defaults  for individual host adapters. For more information, see Chapter 3, “Drives and arrays” on page 41and  Queue depth in  Fibre Channel hosts  topic in the V8.2 Documentation site:  IBM FlashSystem 9100 Knowledge Center - FC Queue Depth IBM FlashSystem 9100 Knowledge Center - iSCSI Queue Depth IBM FlashSystem 9100 Knowledge Center - iSER Queue Depth To prevent hosts from sharing storage inadvertently, establish a storage reservation  mechanism. The mechanisms for restricting access to IBM Spectrum Virtualize volumes use  the SCSI-3 persistent reserve commands or the SCSI-2 reserve and release commands. GLYPH<SM590000> FlashSystem 9100 FC hosts Queue Depth GLYPH<SM590000> FlashSystem 9100 iSCSI hosts Queue Depth GLYPH<SM590000> FlashSystem 9100 iSER hosts Queue Depth 7.5 Host clustering and reserves 7.4.1 Queue depths 7.4 I/O queues 256  IBM FlashSystem 9200 and 9100 Best Practices and Performance Guidelines