SSD for boot disk: 98% health, but only 98 days to live?

[guermantes]

Hi,
Pending the upgrade to 11.2, for which I intend to move from bootdrive on USB-stick to SSD, I have been rummaging about in my drawers (Brits can hold the joke, thank you very much :) ) looking for a suitably sized SSD to re-purpose. I found an Intel 320 40 GB. Next in line is an almost pristine Intel 320 160 GB, but I find it difficult to 'sacrifice' a 160 GB disk.

The 40 GB disk is at 98 % health according to Intel SSD toolbox. Normally, I would find 98 % health very comforting and would go ahead installing Freenas on this drive. However, according to Hard Disk Sentinel, it has only 98+ days to live due to the SMART value 233 Media Wearout Indicator, which has dropped from 100 to 98. It has plenty of host writes and plenty of hours (although nowhere near the MTBF of 1,200,000 Hours). All those hours and all those writes, but still a very high health value. Or the other way around, why does such a small drop in media wearout yield such dire life prospects?

Would you use this drive for a freenas boot drive?

Code:

smartctl 6.6 2016-05-31 r4324 [x86_64-linux-4.15.0-43-generic] (local build)
Copyright (C) 2002-16, Bruce Allen, Christian Franke, www.smartmontools.org

=== START OF INFORMATION SECTION ===
Model Family:     Intel 320 Series SSDs
Device Model:     INTEL SSDSA2CT040G3
Serial Number:    CVPR136308CH040AGN
LU WWN Device Id: 5 001517 959695661
Firmware Version: 4PC10362
User Capacity:    40 020 664 320 bytes [40,0 GB]
Sector Size:      512 bytes logical/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 4
SATA Version is:  SATA 2.6, 3.0 Gb/s
Local Time is:    Sun Jan 20 16:16:36 2019 CET
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:         (    1) seconds.
Offline data collection
capabilities:              (0x75) SMART execute Offline immediate.
                    No Auto Offline data collection support.
                    Abort 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:      (   1) minutes.
Conveyance self-test routine
recommended polling time:      (   1) minutes.
SCT capabilities:            (0x003d)    SCT Status supported.
                    SCT Error Recovery Control supported.
                    SCT Feature Control supported.
                    SCT Data Table supported.

SMART Attributes Data Structure revision number: 5
Vendor Specific SMART Attributes with Thresholds:
ID# ATTRIBUTE_NAME          FLAG     VALUE WORST THRESH TYPE      UPDATED  WHEN_FAILED RAW_VALUE
  3 Spin_Up_Time            0x0020   100   100   000    Old_age   Offline      -       0
  4 Start_Stop_Count        0x0030   100   100   000    Old_age   Offline      -       0
  5 Reallocated_Sector_Ct   0x0032   100   100   000    Old_age   Always       -       0
  9 Power_On_Hours          0x0032   100   100   000    Old_age   Always       -       51053
12 Power_Cycle_Count       0x0032   100   100   000    Old_age   Always       -       75
170 Reserve_Block_Count     0x0033   100   100   010    Pre-fail  Always       -       0
171 Program_Fail_Count      0x0032   100   100   000    Old_age   Always       -       0
172 Erase_Fail_Count        0x0032   100   100   000    Old_age   Always       -       0
183 SATA_Downshift_Count    0x0030   100   100   000    Old_age   Offline      -       0
184 End-to-End_Error        0x0032   100   100   090    Old_age   Always       -       0
187 Reported_Uncorrect      0x0032   100   100   000    Old_age   Always       -       0
192 Unsafe_Shutdown_Count   0x0032   100   100   000    Old_age   Always       -       57
199 CRC_Error_Count         0x0030   100   100   000    Old_age   Offline      -       0
225 Host_Writes_32MiB       0x0032   100   100   000    Old_age   Always       -       91999
226 Workld_Media_Wear_Indic 0x0032   100   100   000    Old_age   Always       -       2104
227 Workld_Host_Reads_Perc  0x0032   100   100   000    Old_age   Always       -       3
228 Workload_Minutes        0x0032   100   100   000    Old_age   Always       -       3063166
232 Available_Reservd_Space 0x0033   100   100   010    Pre-fail  Always       -       0
233 Media_Wearout_Indicator 0x0032   098   098   000    Old_age   Always       -       0
241 Host_Writes_32MiB       0x0032   100   100   000    Old_age   Always       -       91999
242 Host_Reads_32MiB        0x0032   100   100   000    Old_age   Always       -       3053

SMART Error Log Version: 1
No Errors Logged

SMART Self-test log structure revision number 1
Num  Test_Description    Status                  Remaining  LifeTime(hours)  LBA_of_first_error
# 1  Offline             Completed without error       00%     51053         -

SMART Selective self-test log data structure revision number 0
Note: revision number not 1 implies that no selective self-test has ever been run
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.

 

[Yorick]

Hard Disk Sentinel lies. See https://www.thomas-krenn.com/en/wiki/SMART_attributes_of_Intel_SSDs

You've had two full erase cycles on the drive. It's in great shape. That value will decline by 1 with every full erase cycle. As a FreeNAS boot drive, writes will be minimal. I'd go right ahead.