How should I interpret this smartctl readout

I'm running a Debian Jessie Machine with an external 3TB Hard Drive. The drive has gone offline twice in the last few days, trying to [ls] results in nothing to display, same in Dolphin. Running smartctl -a /dev/sdc results in the following. Note that this drive is only a few months old, but it holds my fairly large video collection, managed and Viewed using Plex Media Server. smartctl 6.4 2014-10-07 r4002 [x86_64-linux-3.16.0-4-amd64] (local build) Copyright (C) 2002-14, Bruce Allen, Christian Franke, www.smartmontools.org === START OF INFORMATION SECTION === Model Family: Seagate Barracuda 7200.14 (AF) Device Model: ST3000DM001-1E6166 Serial Number: Z1F4HXVG LU WWN Device Id: 5 000c50 065ca347a Firmware Version: SC48 User Capacity: 3,000,592,982,016 bytes [3.00 TB] Sector Sizes: 512 bytes logical, 4096 bytes physical Rotation Rate: 7200 rpm Form Factor: 3.5 inches Device is: In smartctl database [for details use: -P show] ATA Version is: ATA8-ACS T13/1699-D revision 4 SATA Version is: SATA 3.0, 6.0 Gb/s (current: 3.0 Gb/s) Local Time is: Wed Dec 10 21:04:09 2014 GMT SMART support is: Available - device has SMART capability. SMART support is: Enabled === START OF READ SMART DATA SECTION === SMART Status command failed: scsi error medium or hardware error (serious) SMART overall-health self-assessment test result: PASSED Warning: This result is based on an Attribute check. See vendor-specific Attribute list for marginal Attributes. General SMART Values: Offline data collection status: (0x00) Offline data collection activity was never started. Auto Offline Data Collection: Disabled. Self-test execution status: ( 0) The previous self-test routine completed without error or no self-test has ever been run. Total time to complete Offline data collection: ( 592) seconds. Offline data collection capabilities: (0x73) SMART execute Offline immediate. Auto Offline data collection on/off support. Suspend Offline collection upon new command. No Offline surface scan supported. Self-test supported. Conveyance Self-test supported. Selective Self-test supported. SMART capabilities: (0x0003) Saves SMART data before entering power-saving mode. Supports SMART auto save timer. Error logging capability: (0x01) Error logging supported. General Purpose Logging supported. Short self-test routine recommended polling time: ( 1) minutes. Extended self-test routine recommended polling time: ( 361) minutes. Conveyance self-test routine recommended polling time: ( 2) minutes. SCT capabilities: (0x3081) SCT Status supported. SMART Attributes Data Structure revision number: 10 Vendor Specific SMART Attributes with Thresholds: ID# ATTRIBUTE_NAME FLAG VALUE WORST THRESH TYPE UPDATED WHEN_FAILED RAW_VALUE 1 Raw_Read_Error_Rate 0x000f 113 099 006 Pre-fail Always - 55323488 3 Spin_Up_Time 0x0003 092 091 000 Pre-fail Always - 0 4 Start_Stop_Count 0x0032 100 100 020 Old_age Always - 55 5 Reallocated_Sector_Ct 0x0033 100 100 010 Pre-fail Always - 0 7 Seek_Error_Rate 0x000f 058 052 030 Pre-fail Always - 150347021957 9 Power_On_Hours 0x0032 095 095 000 Old_age Always - 5157 10 Spin_Retry_Count 0x0013 100 100 097 Pre-fail Always - 0 12 Power_Cycle_Count 0x0032 100 100 020 Old_age Always - 48 183 Runtime_Bad_Block 0x0032 099 099 000 Old_age Always - 1 184 End-to-End_Error 0x0032 100 100 099 Old_age Always - 0 187 Reported_Uncorrect 0x0032 100 100 000 Old_age Always - 0 188 Command_Timeout 0x0032 100 100 000 Old_age Always - 0 0 0 189 High_Fly_Writes 0x003a 100 100 000 Old_age Always - 0 190 Airflow_Temperature_Cel 0x0022 056 037 045 Old_age Always In_the_past 44 (Min/Max 41/52 #7782) 191 G-Sense_Error_Rate 0x0032 100 100 000 Old_age Always - 0 192 Power-Off_Retract_Count 0x0032 100 100 000 Old_age Always - 5 193 Load_Cycle_Count 0x0032 096 096 000 Old_age Always - 8971 194 Temperature_Celsius 0x0022 044 063 000 Old_age Always - 44 (0 16 0 0 0) 197 Current_Pending_Sector 0x0012 100 100 000 Old_age Always - 0 198 Offline_Uncorrectable 0x0010 100 100 000 Old_age Offline - 0 199 UDMA_CRC_Error_Count 0x003e 200 200 000 Old_age Always - 0 240 Head_Flying_Hours 0x0000 100 253 000 Old_age Offline - 3274h+33m+50.476s 241 Total_LBAs_Written 0x0000 100 253 000 Old_age Offline - 6233106761 242 Total_LBAs_Read 0x0000 100 253 000 Old_age Offline - 8133666728 SMART Error Log Version: 1 No Errors Logged SMART Self-test log structure revision number 1 No self-tests have been logged. [To run self-tests, use: smartctl -t] SMART Selective self-test log data structure revision number 1 SPAN MIN_LBA MAX_LBA CURRENT_TEST_STATUS 1 0 0 Not_testing 2 0 0 Not_testing 3 0 0 Not_testing 4 0 0 Not_testing 5 0 0 Not_testing Selective self-test flags (0x0): After scanning selected spans, do NOT read-scan remainder of disk. If Selective self-test is pending on power-up, resume after 0 minute delay.