[SOLVED] Which ssd disk is healthier?

[macintos]

Hello everyone...

These are the results using command

smartctl -a /dev/sda

from a linux usb-live system.
Both discs work correctly, without any incident to mention, but I must choose between one of the two.
There is really a big difference between them, because I prefer to choose the 256Gb one, of course, but maybe there is a defect with that model or something?

APPLE SSD SD0128F (Sandisk-based)

Model Family:     Apple SD/SM/TS...E/F SSDs
Device Model:     APPLE SSD SD0128F
Serial Number:    1336A2406996
LU WWN Device Id: 5 001b44 a3109ecd4
Firmware Version: A222821
User Capacity:    121,332,826,112 bytes [121 GB]
Sector Sizes:     512 bytes logical, 4096 bytes physical
Rotation Rate:    Solid State Device
Form Factor:      Unknown (0x0012)
Device is:        In smartctl database [for details use: -P show]
ATA Version is:   ATA8-ACS T13/1699-D revision 6
SATA Version is:  SATA 3.0, 6.0 Gb/s (current: 6.0 Gb/s)
Local Time is:    Tue Aug  6 16:45:47 2019 UTC
SMART support is: Available - device has SMART capability.
SMART support is: Enabled

=== START OF READ SMART DATA SECTION ===
SMART overall-health self-assessment test result: PASSED

General SMART Values:
Offline data collection status:  (0x00)    Offline data collection activity
                    was never started.
                    Auto Offline Data Collection: Disabled.
Total time to complete Offline
data collection:         (    0) seconds.
Offline data collection
capabilities:              (0x00)     Offline data collection not 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.

SMART Attributes Data Structure revision number: 40
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   100   100   000    Pre-fail  Always       -       0
  5 Reallocated_Sector_Ct   0x000f   100   100   000    Pre-fail  Always       -       0
  9 Power_On_Hours          0x0032   100   100   000    Old_age   Always       -       1964
12 Power_Cycle_Count       0x0032   100   100   000    Old_age   Always       -       12907
169 Unknown_Attribute       0x0022   100   100   010    Old_age   Always       -       738908440288
173 Wear_Leveling_Count     0x0022   187   187   100    Old_age   Always       -       906265231668
174 Host_Reads_MiB          0x0030   100   100   000    Old_age   Offline      -       33776019
175 Host_Writes_MiB         0x0030   100   100   000    Old_age   Offline      -       25314071
192 Power-Off_Retract_Count 0x0032   100   100   000    Old_age   Always       -       146
194 Temperature_Celsius     0x0022   035   035   000    Old_age   Always       -       65 (Min/Max 25/82)
197 Current_Pending_Sector  0x0032   000   000   000    Old_age   Always       -       0
199 UDMA_CRC_Error_Count    0x003e   100   100   000    Old_age   Always       -       0
244 Unknown_Attribute       0x0002   000   000   000    Old_age   Always       -       0

SMART Error Log not supported

SMART Self-test Log not supported

Selective Self-tests/Logging not supported

or

APPLE SSD SM0256F (Samsung-based)

Model Family:     Apple SD/SM/TS...E/F/G SSDs
Device Model:     APPLE SSD SM0256F
Serial Number:    S18WNYBD659207
LU WWN Device Id: 5 002538 655584d30
Firmware Version: UXM2EA1Q
User Capacity:    251.000.193.024 bytes [251 GB]
Sector Sizes:     512 bytes logical, 4096 bytes physical
Rotation Rate:    Solid State Device
Device is:        In smartctl database [for details use: -P show]
ATA Version is:   ATA8-ACS T13/1699-D revision 4c
SATA Version is:  SATA 3.0, 6.0 Gb/s (current: 6.0 Gb/s)
Local Time is:    Tue Aug  6 18:34:08 2019 CEST
SMART support is: Available - device has SMART capability.
SMART support is: Enabled

=== START OF READ SMART DATA SECTION ===
SMART overall-health self-assessment test result: PASSED

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:         (    0) seconds.
Offline data collection
capabilities:              (0x5f) SMART execute Offline immediate.
                    Auto Offline data collection on/off support.
                    Abort Offline collection upon new
                    command.
                    Offline surface scan supported.
                    Self-test supported.
                    No 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:      (   2) minutes.
Extended self-test routine
recommended polling time:      (  10) minutes.

SMART Attributes Data Structure revision number: 40
Vendor Specific SMART Attributes with Thresholds:
ID# ATTRIBUTE_NAME          FLAG     VALUE WORST THRESH TYPE      UPDATED  WHEN_FAILED RAW_VALUE
  1 Raw_Read_Error_Rate     0x001a   200   200   000    Old_age   Always       -       0
  5 Reallocated_Sector_Ct   0x0033   100   100   000    Pre-fail  Always       -       0
  9 Power_On_Hours          0x0032   098   098   000    Old_age   Always       -       6683
12 Power_Cycle_Count       0x0032   085   085   000    Old_age   Always       -       14949
169 Unknown_Apple_Attrib    0x0013   253   253   010    Pre-fail  Always       -       2027568500480
173 Wear_Leveling_Count     0x0032   174   174   100    Old_age   Always       -       2276384899741
174 Host_Reads_MiB          0x0022   099   099   000    Old_age   Always       -       10004491
175 Host_Writes_MiB         0x0022   099   099   000    Old_age   Always       -       8406574
192 Power-Off_Retract_Count 0x0012   099   099   000    Old_age   Always       -       2166
194 Temperature_Celsius     0x0022   061   061   000    Old_age   Always       -       39 (Min/Max 11/71)
197 Current_Pending_Sector  0x0022   100   100   000    Old_age   Always       -       0
199 UDMA_CRC_Error_Count    0x001a   200   200   000    Old_age   Always       -       0
240 Unknown_SSD_Attribute   0x0022   100   100   000    Old_age   Always       -       0

SMART Error Log Version: 1
No Errors Logged

I thought maybe you could help me, because I'm a beginner and I'm afraid to choose the worst of the two...

 

[PC Tailor]

Both are just as healthy as one another it would seem.

You could argue the top one is slightly healthier as it's Read and Writes values have not deteriorated and the power on hours is better. But it really is negligble.

I would have made a comment about Wear Levelling Count, however my understanding was these start at 100 and descend, yours are both above 100. So i'm a little confused on that one.

The key points, neither of them have any reallocated sectors, or pending sectors. So you can't really go wrong with either of them in my opinion.

 

[macintos]

Thanks for the quick reply. I am happy to read that I can choose 256GB without fear

Other information I have obtained from macos with the drivedx program about wear leveling count:

Apple SSD SD0128F (SanDisk-based):
SSD Lifetime Left Indicator - 96.7
Wear Leveling Count - 97

### SYSTEM INFORMATION ###
Report Timestamp                     : 6 de agosto de 2019 21:45:14 CEST
Report Timestamp (ISO 8601 format)   : 2019-08-06T21:45:14

Application Name                     : DriveDx
Application Version                  : 1.8.2.610
Application SubBuild                 : 1
Application Edition                  : Standalone
Application Website                  : [url=https://binaryfruit.com/drivedx]https://binaryfruit.com/drivedx[/url]
DriveDx Knowledge Base Revision      : 9/9

Computer Name                        : MacBook Air
Host Name                            : MacBook-Air
Computer Model                       : MacBookAir6,2

OS Boot Time                         : 2019-08-06T21:35:48
Time Since Boot                      : 00h 09m 26s
OS Name                              : macOS
OS Version                           : 10.14.6
OS Build                             : 18G87
OS Kernel Version                    : Darwin 18.7.0

SAT SMART Driver Version             : N/A
ATA Command Support Tolerance        : verypermissive
N of drives with S.M.A.R.T support   : 1



### DRIVE 1 OF 1 ###
Last Checked                         : 6 de agosto de 2019 21:44:45 CEST
Last Checked (ISO 8601 format)       : 2019-08-06T21:44:45

Advanced SMART Status                : OK
Overall Health Rating                : GOOD 100%
Overall Performance Rating           : GOOD 100%
SSD Lifetime Left Indicator          : GOOD 96.7%
Issues found                         : 0

Serial Number                        : 1336A2406996
WWN Id                               : 5 001b44 a3109ecd4
Volumes                              : MacOS
Device Path                          : /dev/disk0
Total Capacity                       : 121.3 GB (121.332.826.112 Bytes)
Model Family                         : Apple (SanDisk-based) SSDs
Model                                : APPLE SSD SD0128F
Firmware Version                     : A222821
Drive Type                           : SSD

Power On Time                        : 1.966 hours (2 months 21 days 22 hours)
Power Cycles Count                   : 12.910
Current Power Cycle Time             : 0.2 hours



=== DEVICE CAPABILITIES ===
S.M.A.R.T. support enabled           : yes
DriveDx Active Diagnostic Config     : Apple (SanDisk-based) f-series SSDs config [ssd.apple.sandisk.f]
Sector Logical Size                  : 512
Sector Physical Size                 : 4096
Physical Interconnect                : PCI
Logical Protocol                     : SATA
Removable                            : no
Ejectable                            : no
ATA Version                          : ATA8-ACS T13/1699-D revision 6
SATA Version                         : SATA 3.0, 6.0 Gb/s (current: 6.0 Gb/s)
I/O Path                             : IOService:/AppleACPIPlatformExpert/PCI0@0/AppleACPIPCI/RP06@1C,5/IOPP/SSD0@0/AppleAHCI/PRT0@0/IOAHCIDevice@0/AppleAHCIDiskDriver/IOAHCIBlockStorageDevice
Attributes Data Structure Revision   : 40
SMART Command Transport (SCT) flags  : 0x0
SCT Status supported                 : no
SCT Feature Control supported        : no
SCT Data Table supported             : no
Error logging capabilities           : 0x1
Self-tests supported                 : no
Offline Data Collection capabilities : 0x0
Offline Data Collection status       : 0x0
Auto Offline Data Collection flags   : 0x0
[Known device                       ]: yes
[Drive State Flags                  ]: 0x0


=== CURRENT POWER CYCLE STATISTICS ===
Data Read                           : 1.1 GB
Data Written                        : 140.1 MB
Data Read/Write Ratio               : 8.12
Average Throughput (Read)           : 15.7 MB/s
Average Throughput (Write)          : 16.3 MB/s

Operations (Read)                   : 61.401
Operations (Write)                  : 11.711
Operations Read/Write Ratio         : 5
Throughput per operation (Read)     : 19.0 KB/Op
Throughput per operation (Write)    : 12.2 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) : 0 (0 / 0)
Warnings (life-span / pre-fail)           : 0 (0 / 0)
I/O Error Count                          : 0 (0 / 0)


=== IMPORTANT HEALTH INDICATORS ===
ID  NAME                                         RAW VALUE                  STATUS
  5 Retired Block Count                          0                          100% OK
173 Wear Leveling Count                          0xD3019E0134               96.7% OK
175 Host Writes MiB                              25.314.211 (24.1 TB)       100% OK
192 Unsafe Shutdown Count                        148                        100% OK
197 Current Pending Block Count                  0                          100% OK
199 UDMA CRC Error Count                         0                          100% OK


=== TEMPERATURE INFORMATION (CELSIUS) ===
Current Temperature                  : 54
Power Cycle Min Temperature          : 54
Power Cycle Max Temperature          : 54
Lifetime Min Temperature             : 44
Lifetime Max Temperature             : 59
Recommended Min Temperature          : 5
Recommended Max Temperature          : 65
Temperature Min Limit                : 5
Temperature Max Limit                : 70


=== DRIVE HEALTH INDICATORS ===
ID   | NAME                                        | TYPE      | UPDATE | RAW VALUE                  | VALUE | THRESHOLD | WORST | LAST MODIFIED        | STATUS         
   1   Raw Read Error Rate                           Pre-fail    online               0x0                100           0    100                       -    100%  OK         
   5   Retired Block Count                           Pre-fail    online                0                 100           0    100                       -    100%  OK         
   9   Power On Hours                                Life-span   online              1.966               100           0    100            6/8/19 21:44    100%  OK         
  12   Power Cycle Count                             Life-span   online              12.910              100           0    100            6/8/19 21:44    100%  OK         
 169   Total Bad Block Count                         Life-span   online           0xAC0A6006E0           100          10    100                       -    100%  OK         
 173   Wear Leveling Count                           Life-span   online           0xD3019E0134           187         100    187           31/7/19 20:49   96.7%  OK         
 174   Host Reads MiB                                Life-span   offline      33.777.228 (32.2 TB)       100           0    100            6/8/19 21:44    100%  OK         
 175   Host Writes MiB                               Life-span   offline      25.314.211 (24.1 TB)       100           0    100            6/8/19 21:44    100%  OK         
 192   Unsafe Shutdown Count                         Life-span   online               148                100           0    100            6/8/19 21:44    100%  OK         
 194   Temperature (Celsius)                         Life-span   online                54                 46          30     46            6/8/19 21:44   22.9%  OK         
 197   Current Pending Block Count                   Life-span   online                0                   0           0      0                       -    100%  OK         
 199   UDMA CRC Error Count                          Life-span   online                0                 100           0    100                       -    100%  OK         
 244   Vendor Specific                               Life-span   online               0x0                  0           0      0                       -    100%  OK         



=== DRIVE ERROR LOG ===
error log is empty


=== DRIVE SELF-TEST LOG ===
self-test log is empty

and

Apple SSD SM0256F (Samsung-based):
SSD Lifetime Left Indicator - 100
Wear Leveling Count - 74

### SYSTEM INFORMATION ###
Report Timestamp                     : 6 de agosto de 2019 21:11:40 CEST
Report Timestamp (ISO 8601 format)   : 2019-08-06T21:11:40

Application Name                     : DriveDx
Application Version                  : 1.8.2.610
Application SubBuild                 : 1
Application Edition                  : Standalone
Application Website                  : [url=https://binaryfruit.com/drivedx]https://binaryfruit.com/drivedx[/url]
DriveDx Knowledge Base Revision      : 9/9

Computer Name                        : MacBook Air
Host Name                            : MacBook-Air
Computer Model                       : MacBookAir6,2

OS Boot Time                         : 2019-08-06T18:50:38
Time Since Boot                      : 02h 21m 02s
OS Name                              : macOS
OS Version                           : 10.14.6
OS Build                             : 18G87
OS Kernel Version                    : Darwin 18.7.0

SAT SMART Driver Version             : N/A
ATA Command Support Tolerance        : verypermissive
N of drives with S.M.A.R.T support   : 1



### DRIVE 1 OF 1 ###
Last Checked                         : 6 de agosto de 2019 20:51:39 CEST
Last Checked (ISO 8601 format)       : 2019-08-06T20:51:39

Advanced SMART Status                : OK
Overall Health Rating                : GOOD 100%
SSD Lifetime Left Indicator          : GOOD 100%
Issues found                         : 0

Serial Number                        : S18WNYBD659207
WWN Id                               : 5 002538 655584d30
Volumes                              : Sin título, Recovery HD
Device Path                          : /dev/disk0
Total Capacity                       : 251.0 GB (251.000.193.024 Bytes)
Model Family                         : Apple (Samsung-based) SSDs
Model                                : APPLE SSD SM0256F
Firmware Version                     : UXM2EA1Q
Drive Type                           : SSD

Power On Time                        : 6.685 hours (9 months 8 days 13 hours)
Power Cycles Count                   : 14.950
Current Power Cycle Time             : 2.4 hours



=== DEVICE CAPABILITIES ===
S.M.A.R.T. support enabled           : yes
DriveDx Active Diagnostic Config     : Apple (Samsung-based) e/f-series SSDs config [ssd.apple.samsung.ef]
Sector Logical Size                  : 512
Sector Physical Size                 : 4096
Physical Interconnect                : PCI
Logical Protocol                     : SATA
Removable                            : no
Ejectable                            : no
ATA Version                          : ATA8-ACS T13/1699-D revision 4c
SATA Version                         : SATA 3.0, 6.0 Gb/s (current: 6.0 Gb/s)
I/O Path                             : IOService:/AppleACPIPlatformExpert/PCI0@0/AppleACPIPCI/RP06@1C,5/IOPP/SSD0@0/AppleAHCI/PRT0@0/IOAHCIDevice@0/AppleAHCIDiskDriver/IOAHCIBlockStorageDevice
Attributes Data Structure Revision   : 40
SMART Command Transport (SCT) flags  : 0x0
SCT Status supported                 : no
SCT Feature Control supported        : no
SCT Data Table supported             : no
Error logging capabilities           : 0x1
Self-tests supported                 : yes
Offline Data Collection capabilities : 0x5f
Offline Data Collection status       : 0x0
Auto Offline Data Collection flags   : 0x0
[Known device                       ]: yes
[Drive State Flags                  ]: 0x0


=== CURRENT POWER CYCLE STATISTICS ===
Data Read                           : 2.6 GB
Data Written                        : 1.6 GB
Data Read/Write Ratio               : 1.68
Average Throughput (Read)           : 50.0 MB/s
Average Throughput (Write)          : 152.9 MB/s

Operations (Read)                   : 164.866
Operations (Write)                  : 38.303
Operations Read/Write Ratio         : 4
Throughput per operation (Read)     : 16.8 KB/Op
Throughput per operation (Write)    : 43.2 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) : 0 (0 / 0)
Warnings (life-span / pre-fail)           : 0 (0 / 0)
Recently failed Self-tests (Short / Full) : 0 (0 / 0)
I/O Error Count                          : 0 (0 / 0)


=== IMPORTANT HEALTH INDICATORS ===
ID  NAME                                         RAW VALUE                  STATUS
  5 Retired Block Count                          0                          100% OK
173 Wear Leveling Count                          0x212031D029D              74.0% OK
175 Host Writes MiB                              8.408.203 (8.0 TB)         99.0% OK
192 Unsafe Shutdown Count                        2.166                      99.0% OK
197 Current Pending Block Count                  0                          100% OK
199 UDMA CRC Error Count                         0                          100% OK


=== TEMPERATURE INFORMATION (CELSIUS) ===
Current Temperature                  : 37
Power Cycle Min Temperature          : 37
Power Cycle Max Temperature          : 41
Lifetime Min Temperature             : 34
Lifetime Max Temperature             : 58
Recommended Min Temperature          : 5
Recommended Max Temperature          : 65
Temperature Min Limit                : 5
Temperature Max Limit                : 70


=== DRIVE HEALTH INDICATORS ===
ID   | NAME                                        | TYPE      | UPDATE | RAW VALUE                  | VALUE | THRESHOLD | WORST | LAST MODIFIED        | STATUS         
   1   Raw Read Error Rate                           Life-span   online               0x0                200           0    200                       -    100%  OK         
   5   Retired Block Count                           Pre-fail    online                0                 100           0    100                       -    100%  OK         
   9   Power On Hours                                Life-span   online              6.685                98           0     98            6/8/19 20:21   98.0%  OK         
  12   Power Cycle Count                             Life-span   online              14.950               85           0     85            6/8/19 18:51   85.0%  OK         
 169   Total Bad Block Count                         Pre-fail    online          0x1D814800F00           253          10    253                       -    100%  OK         
 173   Wear Leveling Count                           Life-span   online          0x212031D029D           174         100    174            4/8/19 22:01   74.0%  OK         
 174   Host Reads MiB                                Life-span   online       10.007.271 (9.5 TB)         99           0     99            6/8/19 20:51   99.0%  OK         
 175   Host Writes MiB                               Life-span   online        8.408.203 (8.0 TB)         99           0     99            6/8/19 20:51   99.0%  OK         
 192   Unsafe Shutdown Count                         Life-span   online              2.166                99           0     99             5/8/19 9:06   99.0%  OK         
 194   Temperature (Celsius)                         Life-span   online                37                 63          30     63            6/8/19 20:21   47.1%  OK         
 197   Current Pending Block Count                   Life-span   online                0                 100           0    100                       -    100%  OK         
 199   UDMA CRC Error Count                          Life-span   online                0                 200           0    200                       -    100%  OK         
 240   Vendor Specific                               Life-span   online               0x0                100           0    100                       -    100%  OK         



=== DRIVE ERROR LOG ===
error log is empty


=== DRIVE SELF-TEST LOG ===
#   | LIFETIME (H)   | TEST TYPE         | PROGRESS | STATUS                          | LBA of 1st error
1           0          Short offline         100%     Completed without error              -     
2           0          Short offline         100%     Completed without error              -     
3           0          Short offline         100%     Completed without error              -     
4           0          Extended offline      100%     Aborted by host                      -     
5           0          Short offline         100%     Completed without error              -     
6           1          Short offline         100%     Completed without error              -     
7           1          Short offline         100%     Completed without error              -     



=== DEVICE STATISTICS ===

[0x01] General Statistics (revision 2)
  0x08 Lifetime Power-on Resets                  : 14.950
  0x10 Power-on Hours                            : 6.685 hours
  0x18 Logical Sectors Written                   : 17.220.000.985 (8.0 TB)
  0x20 Number of Write Commands                  : 182.451.838
  0x28 Logical Sectors Read                      : 20.494.891.802 (9.5 TB)
  0x30 Number of Read Commands                   : 348.984.036

[0x04] General Errors Statistics (revision 1)
  0x08 Number of Reported Uncorrectable Errors   : 0
  0x10 Resets Between Cmd Accept. and Compl.     : 0

[0x06] Transport Statistics (revision 1)
  0x08 Number of Hardware Resets                 : 0
  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 %

I hope this more complete info can give more clarity, and I hope to finally choose the 256GB disk

Thanks again

 

[PC Tailor]

Slightly odd, the SSD Lifetime Left Indicator is a rough indicator out of 100% of how much life is left of the SSD, so this being at 100 would be how a new SSD would look. But the Lifetime usually comes from how much reading and writing has taken place.

But equally the wear levelling count is also a scale up to 100% and it starts at 100 and declines as the usage of the SSD goes up.

I believe samsung based SSDs hold more priority to the wear levelling count, so the fact that this is so much lower, would indicate some potential concern but based on the scheme of things, I don't think you could go wrong either way. Every SSD has Wear, and neither of yours have any bad sectors / reallocations etc.

 

[fzabkar]

Attribute 173 (Wear Leveling Count) appears to be composed of three parts corresponding to the minimum, maximum and average P/E cycles.

These 3 components are best viewed in hexadecimal.

SD0128F

• 0xD3019E0134 -> 0x00D3 / 0x019E / 0x0134 -> 211 (min) / 414 (max) / 308 (avg) <-- raw values
  
  187 / 100 / 187 <- normalised values

SM0256F

• 0x212031D029D -> 0x0212 / 0x031D / 0x029D -> 530 (min) / 797 (max) / 669 (avg) <-- raw values
  
  174 / 100 / 174 <- normalised values

The normalised value appears to assign 1 point per 25 counts, so that the drives record 2500 P/E cycles when they hit the threshold of 100, and 5000 P/E cycles when they hit 0.

For example, in going from 200 to 174, the attribute has lost 26 points, and this corresponds to 650 (= 26 x 25) P/E cycles.

 

[macintos]

Thanks again for the answers.

I'm a little confused because I don't know how to interpret the last comment. Sorry for my difficulty with the technical explanation

Then, I must understand that the SM0256F disk has a higher average durability 669 (compared to 308 of the SD0128F disk) and then have better health or on the contrary I must understand that the use has been greater (used 669 times compared to 308 times) and then have worse health?

I hope I'm not saying something absurd

I'm really grateful for the answers ...

 

[fzabkar]

During its lifetime a flash cell is programmed and erased many times. These events are called P/E cycles (Program/Erase cycles). Eventually the cell wears out. The flash controller maintains a count of the P/E cycles for each block and tries to spread the writes evenly over the whole NAND flash array. This is called wear levelling.

A typical flash technology might be rated for 2500 P/E cycles. SMART attribute 173 reports the number of P/E cycles sustained by the flash blocks. Due to the imperfect nature of wear levelling, some blocks will have been programmed and erased more than others. Hence the min, max and average P/E cycle ( = wear levelling) counts.

Attribute 173 has a normalised value of 200 when the P/E cycle count is 0. That's the max lifetime setting. After an average number of 25 P/E cycles have been recorded, this value drops to 199. When 50 P/E cycles have been recorded, this value drops to 198, and so on. So the drive with the highest normalised value for attribute 173 has sustained the least wear.

 

[fzabkar]

I confess that I don't understand the meaning of attribute 169 (Total Bad Block Count), but it appears to consists of 3 parts. The numbers for the 256GB SSD are approximately twice those of the 128GB SSD. I would think that the attribute must somehow report the total number of available spare blocks and the number which have been used to date.

SD0128F

• 0xAC0A6006E0 -> 0x00AC / 0x0A60 / 0x06E0 -> 172 / 2656 / 1760
  
  100 / 10 / 100

SM0256F

• 0x1D814800F00 -> 0x01D8 / 0x1480 / 0x0F00 -> 472 / 5248 / 3840
  
  253 / 10 / 253

 

[fzabkar]

Here are similar attributes from another Apple SSD:

APPLE SSD TS0256F

https://sourceforge.net/p/smartmontools/mailman/message/32646633/

169 Unknown_Attribute       0x0008   100   100   010    Old_age   Offline      -       1684369576448
173 Erase_Count             0x0010   199   199   100    Old_age   Offline      -       0 32 11

https://www.smartmontools.org/ticket/615

169 Unknown_Attribute       0x0008   100   100   010    Old_age   Offline      -       1851873300992
173 Wear_Leveling_Count     0x0010   197   197   100    Old_age   Offline      -       77315768372 = 18 97 52

The Total Bad Block Count attribute values differ in the first of the 3 words:

• 1,684,369,576,448 = 0x0188 / 0x2C40 / 0x1200
  1,851,873,300,992 = 0x01AF / 0x2C40 / 0x1200

Here is another SMART report for the SD0128F:

https://sourceforge.net/p/smartmontools/mailman/message/32121394/

APPLE SSD SD0128F

169 Unknown_Attribute       -O---K   100   100   010    -    644419159776 = 0x96 / 0x0A60 / 0x06E0
173 Unknown_Attribute       -O---K   200   200   100    -    4296409092 = 1 22 4

 

[fzabkar]

I just remembered this thread:

https://forum.hddguru.com/viewtopic.php?f=10&t=31501

I believe that earlier versions of firmware for the SM0256F (and SM0512F) were affected by a bug in attribute 173. Perhaps the OP's firmware is also buggy?

In fact the 256GB drive has recorded 8.408.203 MB for the Host Writes attribute.

If wear levelling were perfectly averaged, and if the write amplification were 1:1, we would expect that the drive would have recorded 33 P/E cycles, ie an average wear levelling count of 33. Instead it has recorded 669. Something is not right ...

• 8408203 MB / 256 GB = 32.8

 

[macintos]

Thank you very much for the explanations.
Now I understand some of those complicated numbers.

But new doubts appear...

First, if the difference in the value of the Attribute 173 (Wear Leveling Count) would be the most important factor and this could mean different years of use between the two discs.

Second is about something that is commented on in one of the threads, about the importance it has, leaving at least 10% of empty space, because this accelerates the wear of the disk and perhaps it is easier to keep that 10% on the biggest disk.

Third, in the threads it is commented that some error warning seems to be related to the APPLE SSD TS0256F discs when they are used with windows, but in my case I will not use that operating system on this computer, so be safe?

Fourth, Maybe some other factor like temperature, etc ...

Fifth, maybe do the tests that are mentioned in a post of the last thread you mention.

I don't believe there is any real problem. All the similar examples I have found show no evidence of bad blocks or problems in any other SMART attributes.

In fact there are some easy tests that could illuminate the problem.

1/ Write a 10MB file to the drive. Does the raw value of the Total_Host_Writes attribute increase by 10?

2/ Zero-fill the drive. This will erase all the data, so a backup would be mandatory. Does the Total_Host_Writes attribute increase by 512GB? Do the max/min/average raw values of the Wear_Levelling_Count increase by 1?

3/ Perform an ATA Secure Erase. This will send the erase command to the drive, after which the drive will execute it internally, without further intervention by the host. Does the Total_Host_Writes attribute remain unchanged? Do the max/min/average raw values of the Wear_Levelling_Count increase by 1?

Note that an encrypted drive will execute an ATA Secure Erase command by simply throwing away the encryption key, in which case test #3 will require only a few seconds and should not change the SMART values.

but maybe it's too complicated for me, and since have to erase all the content, I'm not sure how to get back on disk the original recovery partition of the macbook air mid 2013...

So, considering a similar use in the two discs and considering all the factors mentioned so far, which would be the best choice?

Thank you very much again for all the help

 

[fzabkar]

I don't trust that Samsung model, even though it would have the least wear (after we have adjusted the SMART data to account for a possible firmware bug).

That said, here is a disturbing tech blog about Samsung's 840 EVO. I'm wondering whether your SSD uses the same bad memory, and if the excessive P/E cycles are due to the constant "refreshing" action of a firmware "fix".

Samsung 840 EVO - how to easily lose your data forever:
https://forum.acelaboratory.com/viewtopic.php?t=8735

I spoke with our ACE Lab developers and did you know what we found? Everything is very simple - NAND memory in Samsung 840 EVO is TLC based, and it is VERY VERY Bad. After some time when you write the data on memory, the charge inside NAND cells is flow away. The voltage inside cells become worse and worse, and finally - flow away forever. It means that if you will not use your 840 EVO drive for some time, you will find that your SSD is EMPTY.

You ask me - are the guys from Samsung didn't know about that issue? Why they did not find the way to fix this bug?!
And I will answer - they release new FW, which make very simple thing - in background, when you working with your laptop or with PC, it just rewrite customer data again and again, again and gain by cycle, every time with the only goal - to keep the data and charges inside cells "fresh". When drive is not connected to power source, charge from cells is flowing away.

Of course this bug fix is not solve the main problem - bad quality of NAND memory. That's why after 840 EVO, Samsung decided to release new generation - Samsung 850 EVO\PRO and Samsung 950 for laptops - in new generations they cancelled TLC memory, and decided to use new 3DNand memory chips with better quality.

 

[macintos]

Thanks again for the help, looks like that last link is revealing...

Well, then I'll have to pick the 128gb.

Finally, I have some doubts. Is there any way to know exactly that this model or unit has that problem? Maybe the results of the tests I've already done reveal it, but what is that exact results?

Or would it be necessary to do any other tests, which confirm without doubt, that this disk is affected by this problem?

Maybe we already have enough evidence to forget about that disk and it's better to stop spending more time on this issue and choose the 128 gb sandisk. I understand that your decison is definitely choosing the 128gb and I sincerely appreciate your opinion.

This Samsung 256gb disk has been used for 1 year daily and I haven't noticed any incidence and I think that's why I'm insecure, but maybe I've been ignoring a problem that could appear at any time and lose the data.

Thank you so much again

 

[fzabkar]

I really don't know which SSD to choose, but I'm wary of the Samsung.

 

[PC Tailor]

I think it goes back to the earlier point:

I don't think you could go wrong either way. Every SSD has Wear, and neither of yours have any bad sectors / reallocations.

Point is there is no obvious signs of anything critically wrong with either.

 

[macintos]

Excuse me guys, I may not have correctly understood all the meaning because of my bad English

I hope I have not been a cause of great confusion

Of course the last decision is mine and I appreciate all the comments you have shared. Thanks to them I now have more clarity and knowledge about some aspects related to an SSD disk.

Thank you very much and I will definitely return whenever I have new questions and I will recommend this fantastic forum

see you soon