Chosen Solution

In 2020, I purchased a brand new 2017 5K iMac which enclosed a 2Tb fusion drive, that is a 128Gb Apple (Samsung) NVMe SSD + a 2Tb Seagate HDD. 16 months later, the fusion drive crashed due to the hard drive being crippled with bad sectors. Stuff happens, I thought… I changed the original NVME for a 2Tb Samsung 970 EVO plus, and the original hard drive for a Samsung 870 EVO, both disks being highly rated everywhere. Everything went fine for 15 months, but suddenly, the 970 EVO plus on which MacOS was installed locked itself into read-only mode because 100% of its SSD spare blocks had been used. Drive DX reports more than 5000 media and data integrity errors, for just above 16 Tb written. The 870 EVO seems about to follow the same course, with 1040 spare blocks used, (50% of available spare blocks), and a flash read fail count in the thousands, for just 5Tb written !!! My question is : What is the most likely cause for this behaviour ? Has anyone had such a bad experience with an iMac ?

Yep that is what I often encounter when using an M.2 blade SSD instead of the proper Apple designed SSD or one of the 3rd parties which properly design the SSD for the sound up to emulate the Apple unit. So you’ll need to take the Samsung 970 EVO plus out and put in its place either iMac Intel 27" (Mid 2017-2019) SSD Blade Upgrade Bundle or Custom Samsung 2TB SSPOLARIS SSD The error condition can also be due to the Fusion Drive setup was not cleared fully as you really don’t want it with a dual SSD setup.

Meanwhile, first Drive Dx export for the 970 Evo + drive : SYSTEM INFORMATION ### Report Timestamp : 5 octobre 2022 22:38:09 UTC+2 Report Timestamp (ISO 8601 format) : 2022-10-05T22:38:09 Application Name : DriveDx Application Version : 1.11.0.730 Application SubBuild : 0 Application Edition : Standalone Application Website : https://binaryfruit.com/drivedx DriveDx Knowledge Base Revision : 101/101 Computer Name : myMac Host Name : myMac Computer Model : iMac18,3 OS Boot Time : 2022-10-04T21:51:51 Time Since Boot : 1 day 00h 46m 18s OS Name : macOS OS Version : 10.16.0 OS Build : 21G115 OS Kernel Version : Darwin 21.6.0 SAT SMART Driver Version : N/A ATA Command Support Tolerance : verypermissive N of drives in report : 1 DRIVE 1 OF 1 ### Last Checked : 5 octobre 2022 22:22:51 UTC+2 Last Checked (ISO 8601 format) : 2022-10-05T22:22:51 Advanced SMART Status : FAILING Overall Health Rating : BAD 0% SSD Lifetime Left Indicator : GOOD 100% Issues found : 4 Serial Number : xxxxxxxxxxxxx WWN Id : Volumes : Macintosh SSD Device Path : /dev/disk0 Total Capacity : 2.0 TB (2 000 398 934 016 Bytes) Model Family : Samsung 970 EVO Series SSD Model : Samsung SSD 970 EVO Plus 2TB Firmware Version : 3B2QEXM7 Drive Type : SSD Power On Time : 7 139 hours (9 months 27 days 11 hours) Power Cycles Count : 5 611 Current Power Cycle Time : 24.8 hours DEVICE CAPABILITIES S.M.A.R.T. support enabled : yes DriveDx Active Diagnostic Config : Samsung 970 EVO Series SSD config [ssd.nvme.samsung.970.evo.01] Sector Logical Size : 512 Sector Physical Size : 512 Physical Interconnect : PCI-Express (PCIe) Logical Protocol : NVM-Express (NVMe) Removable : no Ejectable : no NVMe Revision Supported : 1.30 PCI Vendor Id : 0x144d Thermal Throttling Supported : no Volatile Write Cache Supported : yes Maximum Data Transfer Size : 128 Pages Log Page Attributes : 0xf Format NVM Attributes : 0x5 Optional Admin Command Support : 0x0 Optional NVM Command Support : 0x57 (Compare, Wr_Unc, DS_Mngmt, Save/Sel_Feat, +) Number of Power States Supported : 4 Error Log Page Entries : 63 Keep Alive Support : 0 Total NVMe Capacity : 2 000 398 934 016 (2.0 TB) Unallocated NVMe Capacity : - Number of NVMe Namespaces : 1 I/O Path : IOService:/AppleACPIPlatformExpert/PCI0@0/AppleACPIPCI/RP17@1B/IOPP/SSD0@0/IONVMeController/IONVMeBlockStorageDevice@1 [Known device ]: yes [Drive State Flags ]: 0x2000014 CURRENT POWER CYCLE STATISTICS Time since computer startup : 24 hours Data Read : 440 983 040 bytes (441.0 MB) Data Written : 0 bytes (0 B) Data Read/hour : 17.8 MB/hour Data Write/hour : 0 B/hour Operations (Read) : 103 771 Read IOPS : 7 156 Operations (Write) : 0 Write IOPS : 0 Throughput per operation (Read) : 4.2 KB/Op Latency Time (Read) : 0 ns Latency Time (Write) : 0 ns Retries (Read) : 0 Retries (Write) : 0 Errors (Read) : 0 Errors (Write) : 0 PROBLEMS SUMMARY Failed Indicators (life-span / pre-fail) : 0 (0 / 0) Failing Indicators (life-span / pre-fail) : 2 (0 / 2) Warnings (life-span / pre-fail) : 0 (0 / 0) I/O Error Count : 0 (0 / 0) IMPORTANT HEALTH INDICATORS ID NAME RAW VALUE STATUS 7 Data Units Written 31 617 078 (16.2 TB) 100% OK 14 Media and Data Integrity Errors 5 339 100% Failing TEMPERATURE INFORMATION (CELSIUS) Current Temperature : 51 Power Cycle Min Temperature : 21 Power Cycle Max Temperature : 51 Lifetime Min Temperature : 21 Lifetime Max Temperature : 52 Recommended Min Temperature : 5 Recommended Max Temperature : 82 Temperature Min Limit : 5 Temperature Max Limit : 85 DRIVE HEALTH INDICATORS ID | NAME | TYPE | UPDATE | RAW VALUE | VALUE | THRESHOLD | WORST | LAST MODIFIED | STATUS 2 Composite Temperature Life-span online 51 (51 °C) 49 15 49 05/10/2022 22:22 40.0% OK 3 Available Spare Pre-fail online 0 0 10 0 20/09/2022 21:41 0% Failing 5 Life Percentage Used Life-span online 0 100 0 100 - 100% OK 6 Data Units Read Life-span online 104 257 933 (53.4 TB) 100 0 100 05/10/2022 22:22 100% OK 7 Data Units Written Life-span online 31 617 078 (16.2 TB) 100 0 100 20/09/2022 21:41 100% OK 8 Host Read Commands Life-span online 1 649 199 428 100 0 100 05/10/2022 22:22 100% OK 9 Host Write Commands Life-span online 755 316 185 100 0 100 20/09/2022 21:41 100% OK 10 Controller Busy Time Life-span online 3 289 (3 289 minutes) 100 0 100 30/09/2022 12:44 100% OK 11 Power Cycles Life-span online 5 611 100 0 100 05/10/2022 21:01 100% OK 12 Power On Hours Life-span online 7 139 (7 139 hours) 100 0 100 05/10/2022 22:22 100% OK 13 Unsafe Shutdowns Life-span online 487 100 0 100 05/10/2022 21:01 100% OK 14 Media and Data Integrity Errors Pre-fail online 5 339 100 0 100 30/09/2022 12:44 100% Failing 15 Error Information Log Entries Pre-fail online 0 100 0 100 30/09/2022 12:44 100% OK 16 Warning Composite Temperature Time Life-span online 0 (0 minutes) 100 0 100 - 100% OK 17 Critical Composite Temperature Time Life-span online 0 (0 minutes) 100 0 100 - 100% OK 101 Temperature Sensor 1 Life-span online 51 (51 °C) 49 15 49 05/10/2022 22:22 40.0% OK 102 Temperature Sensor 2 Life-span online 76 (76 °C) 24 15 24 05/10/2022 22:22 10.6% OK DRIVE ERROR LOG error log is empty

And second output of DriveDx for the 870 EVO : SYSTEM INFORMATION ### Report Timestamp : 5 octobre 2022 22:38:16 UTC+2 Report Timestamp (ISO 8601 format) : 2022-10-05T22:38:16 Application Name : DriveDx Application Version : 1.11.0.730 Application SubBuild : 0 Application Edition : Standalone Application Website : https://binaryfruit.com/drivedx DriveDx Knowledge Base Revision : 101/101 Computer Name : myMac Host Name : myMac Computer Model : iMac18,3 OS Boot Time : 2022-10-04T21:51:51 Time Since Boot : 1 day 00h 46m 25s OS Name : macOS OS Version : 10.16.0 OS Build : 21G115 OS Kernel Version : Darwin 21.6.0 SAT SMART Driver Version : N/A ATA Command Support Tolerance : verypermissive N of drives in report : 1 DRIVE 1 OF 1 ### Last Checked : 5 octobre 2022 22:22:51 UTC+2 Last Checked (ISO 8601 format) : 2022-10-05T22:22:51 Advanced SMART Status : FAILING Overall Health Rating : AVERAGE 48.9% Overall Performance Rating : GOOD 100% SSD Lifetime Left Indicator : GOOD 100% Issues found : 3 Serial Number : xxxxxxxxxxxxxxx WWN Id : 5 002538 f71201c25 Volumes : Stockage Device Path : /dev/disk1 Total Capacity : 2.0 TB (2 000 398 934 016 Bytes) Model Family : Samsung SSD Model : Samsung SSD 870 EVO 2TB Form Factor : 2.5 inches Firmware Version : SVT01B6Q Drive Type : SSD Power On Time : 7 042 hours (9 months 23 days 10 hours) Power Cycles Count : 5 626 Current Power Cycle Time : 24.8 hours DEVICE CAPABILITIES S.M.A.R.T. support enabled : yes DriveDx Active Diagnostic Config : Samsung SSDs default config [ssd.samsung.common] Sector Logical Size : 512 Sector Physical Size : 512 Physical Interconnect : SATA Logical Protocol : SATA Removable : no Ejectable : no ATA Version : ACS-4 T13/BSR INCITS 529 revision 5 SATA Version : SATA 3.3, 6.0 Gb/s (current: 6.0 Gb/s) I/O Path : IOService:/AppleACPIPlatformExpert/PCI0@0/AppleACPIPCI/SATA@17/AppleIntelPchSeriesAHCI/PRT0@0/IOAHCIDevice@0/AppleAHCIDiskDriver/IOAHCIBlockStorageDevice Attributes Data Structure Revision : 1 SMART Command Transport (SCT) flags : 0x3d SCT Status supported : yes SCT Feature Control supported : yes SCT Data Table supported : yes Error logging capabilities : 0x1 Self-tests supported : yes Offline Data Collection capabilities : 0x53 Offline Data Collection status : 0x0 Auto Offline Data Collection flags : 0x0 [Known device ]: yes [Drive State Flags ]: 0x6000100 [Last State Change Timestamp ]: 2022-10-04T22:12:51 [Last State Change Flags ]: 0x6000100 [Last State Change Diff Flags ]: 0x2000 Last Email Report Timestamp : 2022-10-04T22:12:51 Last Email Report Reason Flags : 0x6000100 Last Email Report State Change Flags : 0x2000 CURRENT POWER CYCLE STATISTICS Time since computer startup : 24 hours Data Read : 4 375 301 632 bytes (4.4 GB) Data Written : 5 003 427 840 bytes (5.0 GB) Data Read/Write Ratio : 0.87 Data Read/hour : 176.6 MB/hour Data Write/hour : 202.0 MB/hour Operations (Read) : 331 333 Read IOPS : 4 234 Operations (Write) : 66 215 Write IOPS : 846 Operations Read/Write Ratio : 5 Throughput per operation (Read) : 13.2 KB/Op Throughput per operation (Write) : 75.6 KB/Op Latency Time (Read) : 0 ns Latency Time (Write) : 0 ns Retries (Read) : 0 Retries (Write) : 0 Errors (Read) : 0 Errors (Write) : 0 PROBLEMS SUMMARY Failed Indicators (life-span / pre-fail) : 0 (0 / 0) Failing Indicators (life-span / pre-fail) : 2 (1 / 1) Warnings (life-span / pre-fail) : 0 (0 / 0) Recently failed Self-tests (Short / Full) : 1 (0 / 1) I/O Error Count : 0 (0 / 0) Time in Under temperature : 0 minutes Time in Over temperature : 0 minutes IMPORTANT HEALTH INDICATORS ID NAME RAW VALUE STATUS 5 Retired Block Count 1 040 48.9% Failing 177 Wear Leveling Count 7 99.0% OK 179 Used Reserved Block Count Total 1 040 48.9% OK 181 Program Fail Count 0 100% OK 182 Erase Fail Count 0 100% OK 241 Total LBAs Written 9 916 669 207 (5.1 TB) 99.0% OK TEMPERATURE INFORMATION (CELSIUS) Current Temperature : 30 Power Cycle Min Temperature : 19 Power Cycle Max Temperature : 28 Lifetime Min Temperature : 19 Lifetime Max Temperature : 55 Recommended Min Temperature : 0 Recommended Max Temperature : 70 Temperature Min Limit : 0 Temperature Max Limit : 70 DRIVE HEALTH INDICATORS ID | NAME | TYPE | UPDATE | RAW VALUE | VALUE | THRESHOLD | WORST | LAST MODIFIED | STATUS 5 Retired Block Count Pre-fail online 1 040 54 10 54 04/10/2022 22:12 48.9% Failing 9 Power On Hours Life-span online 7 042 98 0 98 05/10/2022 22:22 98.0% OK 12 Power Cycle Count Life-span online 5 626 94 0 94 05/10/2022 21:01 94.0% OK 177 Wear Leveling Count Pre-fail online 7 99 0 99 04/10/2022 22:12 99.0% OK 179 Used Reserved Block Count Total Pre-fail online 1 040 54 10 54 04/10/2022 22:12 48.9% OK 181 Program Fail Count Life-span online 0 100 10 100 - 100% OK 182 Erase Fail Count Life-span online 0 100 10 100 - 100% OK 183 Total Runtime Bad Block Count Pre-fail online 1 040 54 10 54 04/10/2022 22:12 48.9% OK 187 Flash Read Fail Count Life-span online 1 258 99 0 99 27/09/2022 21:02 99.0% Failing 190 Airflow Temperature Celsius Life-span online 30 70 30 45 05/10/2022 22:22 57.1% OK 195 Hardware ECC Recovered Life-span online 0x4EA 199 0 199 04/10/2022 22:12 99.5% OK 199 UDMA CRC Error Count Life-span online 0 100 0 100 - 100% OK 235 Power Recovery Count Life-span online 64 99 0 99 01/10/2022 23:10 99.0% OK 241 Total LBAs Written Life-span online 9 916 669 207 (5.1 TB) 99 0 99 05/10/2022 11:13 99.0% OK DRIVE ERROR LOG

| TIME OCCURRED | ERRORS | PRIOR COMMAND

5 6973 hours UNC READ LOG EXT 4 6973 hours UNKNOWN ERROR READ LOG EXT 3 6973 hours UNKNOWN ERROR READ LOG EXT 2 6973 hours UNKNOWN ERROR READ LOG EXT 1 6973 hours UNKNOWN ERROR READ FPDMA QUEUED DRIVE SELF-TEST LOG

| LIFETIME (H) | TEST TYPE | PROGRESS | STATUS | LBA of 1st error

1 7001 Short offline 100% Completed without error - 2 7001 Extended offline 10% Completed: read failure 90481528 3 7001 Extended offline 10% Completed: read failure 90481528 4 7001 Extended offline 10% Completed: read failure 90481528 5 7001 Extended offline 10% Completed: read failure 90481528 6 7001 Extended offline 10% Completed: read failure 90481528 7 7000 Extended offline 10% Completed: read failure 90481528 8 6999 Short offline 100% Completed without error - 9 6997 Extended offline 10% Completed: read failure 90481528 10 6996 Extended offline 10% Completed: read failure 90481528 11 6996 Short offline 100% Completed without error - 12 6966 Short offline 100% Completed without error - 13 4 Short offline 100% Completed without error - DEVICE STATISTICS [0x01] General Statistics (revision 1) 0x08 Lifetime Power-on Resets : 5 626 0x10 Power-on Hours : 7 042 hours 0x18 Logical Sectors Written : 9 916 669 207 (5.1 TB) 0x20 Number of Write Commands : 14 992 569 0x28 Logical Sectors Read : 11 135 129 380 (5.7 TB) 0x30 Number of Read Commands : 91 682 968 0x38 Date and Time TimeStamp : 1 253 000 ms [0x04] General Errors Statistics (revision 1) 0x08 Number of Reported Uncorrectable Errors : 1 258 0x10 Resets Between Cmd Accept. and Compl. : 0 [0x05] Temperature Statistics (revision 1) 0x08 Current Temperature : 30 °C 0x20 Highest Temperature : 55 °C 0x28 Lowest Temperature : 19 °C 0x58 Specified Max Operating Temperature : 70 °C [0x06] Transport Statistics (revision 1) 0x08 Number of Hardware Resets : 6 492 0x10 Number of ASR Events : 0 0x18 Number of Interface CRC Errors : 0 [0x07] Solid State Drive Statistics (revision 1) 0x08 Percentage Used Endurance Indicator : 0 %