Why does multipathd daemon report failed paths?

Issue

• Multipathd is reporting failed paths. Found following error messages in /var/log/messages file

    May  6 10:49:01 hostname kernel: sd 1:0:1:0: emc: at SP A Port 3 (owned, default SP A)
    May  6 10:49:01 hostname multipathd: dm-9: add map (uevent)
    May  6 10:49:01 hostname multipathd: dm-9: devmap already registered
    May  6 10:49:01 hostname kernel: sd 0:0:1:0: Device not ready: <6>: Current: sense key: Not Ready
    May  6 10:49:01 hostname kernel:     Add. Sense: Logical unit not ready, manual intervention required
    May  6 10:49:01 hostname kernel:
    May  6 10:49:01 hostname kernel: end_request: I/O error, dev sdl, sector 16549394
    May  6 10:49:01 hostname kernel: device-mapper: multipath: Failing path 8:176.
    May  6 10:49:01 hostname multipathd: dm-9: add map (uevent)
    May  6 10:49:01 hostname multipathd: dm-9: devmap already registered

Found following messages in dmesg :

    end_request: I/O error, dev sdx, sector 24827154
    device-mapper: multipath: Failing path 65:112.
    sd 1:0:1:0: emc: long trespass command sent
    sd 1:0:1:0: emc: at SP A Port 3 (owned, default SP A)
    sd 0:0:0:0: emc: at SP A Port 2 (owned, default SP A)
    sd 0:0:1:0: emc: long trespass command sent
    sd 0:0:1:0: emc: at SP B Port 3 (owned, default SP A)
    sd 1:0:0:0: emc: at SP B Port 2 (owned, default SP A)
    sd 0:0:0:0: Device not ready: <6>: Current: sense key: Not Ready
    Add. Sense: Logical unit not ready, manual intervention required