Changes between Version 68 and Version 69 of FAQ


Ignore:
Timestamp:
Nov 11, 2017, 3:18:53 PM (6 years ago)
Author:
Christian Franke
Comment:

Add info about self-test duration

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  • FAQ

    v68 v69  
    411411----
    412412
     413=== Why do self-tests take very long? ===
     414=== Why is the system very slow during a self-test? ===
     415
     416The `smartctl -t TEST` command (or `smartd.conf -s` directive) issues a command to start a test
     417(ATA: ''SMART EXECUTE OFF-LINE IMMEDIATE'', SCSI: ''SEND DIAGNOSTIC'').
     418The self-tests are controlled by drive firmware.
     419There is no related data transfer between host and drive during a test.
     420The interleaving of regular I/O and read tests depends on the specific implementation in the firmware.
     421
     422Many implementations work reasonably.
     423Some slow down the self-test even on average system load such that the test virtually never ends.
     424Others slow down regular I/O such that the system is unusable during a test.
     425
     426----
     427
     428=== Why do self-tests take much longer than predicted? ===
     429
     430The predicted completion time printed by `smartctl -t TEST` is based on values returned by drive firmware
     431(ATA: ''SELF-TEST ROUTINE RECOMMENDED POLLING TIME'' from ''SMART DATA STRUCTURE'',
     432SCSI: ''EXTENDED SELF-TEST COMPLETION TIME'' from ''CONTROL MODE PAGE'').
     433The prediction assumes that no regular I/O is done during the test.
     434
     435----
     436
    413437=== Why are long self-tests keep getting interrupted? ===
    414438