# # check changed state of the LVM schedular # lslv test_lv_1 LOGICAL VOLUME: test_lv_1 VOLUME GROUP: test_vg_1 LV IDENTIFIER: 00f6600100004c00000001464e967f3d.1 PERMISSION: read/write VG STATE: active/complete LV STATE: closed/syncd TYPE: jfs2 WRITE VERIFY: off MAX LPs: 3096 PP SIZE: 64 megabyte(s) COPIES: 2 SCHED POLICY: parallel/sequential LPs: 3096 PPs: 6192 STALE PPs: 0 BB POLICY: relocatable INTER-POLICY: minimum RELOCATABLE: yes INTRA-POLICY: middle UPPER BOUND: 16 MOUNT POINT: /test/preferred_read LABEL: /test/preferred_read DEVICE UID: 0 DEVICE GID: 0 DEVICE PERMISSIONS: 432 MIRROR WRITE CONSISTENCY: on/ACTIVE EACH LP COPY ON A SEPARATE PV ?: yes Serialize IO ?: NO INFINITE RETRY: no PREFERRED READ: 1 # lslv test_lv_1 | grep SCHED POLICY COPIES: 2 SCHED POLICY: parallel/sequential # # mount file system # mount /test/preferred_read # # write some data to the filesystem /test/preferred_read # # then read this data and check with iostat Disks: % tm_act Kbps tps Kb_read Kb_wrtn hdisk1 0.0 147495.2 1036.4 737476 0 hdisk2 0.0 134964.8 736.6 674824 0 hdisk4 0.0 85035.2 448.6 425176 0 hdisk3 0.0 118422.4 684.2 592112 0 The setup of the logical volume is now preferred read from the first copy. Check which logical volumes are primary, which are secondary, and which are tertiary, if any.  This list might be a long list. The first 10 lines of the command output and a command for a  quick overview are shown in Example 6-8. Setting preferred read to the FlashSystem 900 Example 6-8 Get first, second, and third logical volume physical disk #  # # Get first, second, and third logical volume's physical disk # # Get reduced list of all involved hdisks # # list used Physical volume names # lslv -m test_lv_1 | awk '{print $3, "	", $5, "	", $7}' | uniq PV1 PV2  PV3 hdisk1 hdisk5 hdisk2 hdisk6 hdisk3 hdisk7 hdisk4 hdisk8  # # check which copy is selected for primary # lslv test_lv_1 | grep PREFERRED INFINITE RETRY: no PREFERRED READ: 1 180  Implementing IBM FlashSystem 900 Model AE3