# # 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. 

## Setting preferred read to the FlashSystem 900 

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. 

# # # 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 

