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My Ubuntu RAID configuration changes during a reboot and I don't understand why.

  • Problem 1: /dev/md/host:name device is not created at boot. I don't understand how, when, or why the descriptive names are created and it would be better if it were more predictable.

This array always gets a device name:

jak # mdadm --detail /dev/md127
[...]
Name : jak:neat  (local to host jak)
UUID : 593fc406:87eefd53:0a076a84:f1405112

This array almost never gets a device name:

jak # mdadm --detail /dev/md130
[...]
Name : jak:sour  (local to host jak)
UUID : 809a185b:a2613844:3975b412:759ec297

My understanding is that the purpose of these human-readable names is for use in /etc/fstab:

jak # tail -2 /etc/fstab 
/dev/md130 /jak/data/sour ext4 defaults 0 0
/dev/md/jak:neat /jak/data/neat ext4 defaults 0 0

You can see that for jak:sour I am mounting /dev/md130 explicitly which is problematic since that device name changes occasionally. I also don't understand why the device number changes. What is the reliable /dev entry that I should use in fstab?

  • Problem 2: My spare drives fall out of the arrays each reboot.

Both jak:neat and jak:sour have spare drives (mdadm output is below). After every reboot, the spare drives vanish from the arrays. The disk devices do appear in /dev/sd* and I can re-attach them to the arrays easily enough (mdadm --add /dev/md127 /dev/sdn1) but obviously I'd rather they not fall out of the array.

  • Groveling: Google and Stack Exchange searches for specific linux software raid array problems is kind of a miserable exercise in signal to noise. I hope these are good questions to ask.

  • Config details:

# uname -a
Linux jak 4.15.0-65-generic #74-Ubuntu SMP Tue Sep 17 17:06:04 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux

jak # mdadm --detail /dev/md127
/dev/md127:
           Version : 1.2
     Creation Time : Fri Jun  1 07:33:21 2018
        Raid Level : raid10
        Array Size : 23441682432 (22355.73 GiB 24004.28 GB)
     Used Dev Size : 7813894144 (7451.91 GiB 8001.43 GB)
      Raid Devices : 6
     Total Devices : 7
       Persistence : Superblock is persistent

     Intent Bitmap : Internal

       Update Time : Sun Oct  6 07:02:47 2019
             State : clean, checking 
    Active Devices : 6
   Working Devices : 7
    Failed Devices : 0
     Spare Devices : 1

            Layout : near=2
        Chunk Size : 512K

Consistency Policy : bitmap

      Check Status : 18% complete

              Name : jak:neat  (local to host jak)
              UUID : 593fc406:87eefd53:0a076a84:f1405112
            Events : 201984

    Number   Major   Minor   RaidDevice State
       0       8       17        0      active sync set-A   /dev/sdb1
       1      65        1        1      active sync set-B   /dev/sdq1
       2       8       81        2      active sync set-A   /dev/sdf1
       3      65       33        3      active sync set-B   /dev/sds1
       4       8       49        4      active sync set-A   /dev/sdd1
       6      65       17        5      active sync set-B   /dev/sdr1

       7       8      177        -      spare   /dev/sdl1
jak # 

jak # mdadm --detail /dev/md130
/dev/md130:
           Version : 1.2
     Creation Time : Sat May 26 10:51:23 2018
        Raid Level : raid6
        Array Size : 39065217024 (37255.49 GiB 40002.78 GB)
     Used Dev Size : 9766304256 (9313.87 GiB 10000.70 GB)
      Raid Devices : 6
     Total Devices : 7
       Persistence : Superblock is persistent

     Intent Bitmap : Internal

       Update Time : Sun Oct  6 07:03:43 2019
             State : clean, checking 
    Active Devices : 6
   Working Devices : 7
    Failed Devices : 0
     Spare Devices : 1

            Layout : left-symmetric
        Chunk Size : 512K

Consistency Policy : bitmap

      Check Status : 41% complete

              Name : jak:sour  (local to host jak)
              UUID : 809a185b:a2613844:3975b412:759ec297
            Events : 139649

    Number   Major   Minor   RaidDevice State
       0       8        1        0      active sync   /dev/sda1
       1       8       33        1      active sync   /dev/sdc1
       2       8      129        2      active sync   /dev/sdi1
       3       8      145        3      active sync   /dev/sdj1
       4       8      161        4      active sync   /dev/sdk1
       6       8      241        5      active sync   /dev/sdp1

       7       8      209        -      spare   /dev/sdn1
jak #

I don't suspect /dev/sdn is suspicious but here are the details anyway.

jak # smartctl -a /dev/sdn
smartctl 6.6 2016-05-31 r4324 [x86_64-linux-4.15.0-65-generic] (local build)
Copyright (C) 2002-16, Bruce Allen, Christian Franke, www.smartmontools.org

=== START OF INFORMATION SECTION ===
Device Model:     WDC WD100EFAX-68LHPN0
Serial Number:    JEKG3TLZ
LU WWN Device Id: 5 000cca 267f04f25
Firmware Version: 83.H0A83
User Capacity:    10,000,831,348,736 bytes [10.0 TB]
Sector Sizes:     512 bytes logical, 4096 bytes physical
Rotation Rate:    5400 rpm
Form Factor:      3.5 inches
Device is:        Not in smartctl database [for details use: -P showall]
ATA Version is:   ACS-2, ATA8-ACS T13/1699-D revision 4
SATA Version is:  SATA 3.2, 6.0 Gb/s (current: 6.0 Gb/s)
Local Time is:    Sun Oct  6 07:04:58 2019 PDT
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:  (0x82) Offline data collection activity
                    was completed without error.
                    Auto Offline Data Collection: Enabled.
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:        (   93) seconds.
Offline data collection
capabilities:            (0x5b) SMART execute Offline immediate.
                    Auto Offline data collection on/off support.
                    Suspend 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:    (1116) 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: 16
Vendor Specific SMART Attributes with Thresholds:
ID# ATTRIBUTE_NAME          FLAG     VALUE WORST THRESH TYPE      UPDATED  WHEN_FAILED RAW_VALUE
  1 Raw_Read_Error_Rate     0x000b   100   100   016    Pre-fail  Always       -       0
  2 Throughput_Performance  0x0004   131   131   054    Old_age   Offline      -       104
  3 Spin_Up_Time            0x0007   100   100   024    Pre-fail  Always       -       0
  4 Start_Stop_Count        0x0012   100   100   000    Old_age   Always       -       3
  5 Reallocated_Sector_Ct   0x0033   100   100   005    Pre-fail  Always       -       0
  7 Seek_Error_Rate         0x000a   100   100   067    Old_age   Always       -       0
  8 Seek_Time_Performance   0x0004   128   128   020    Old_age   Offline      -       18
  9 Power_On_Hours          0x0012   100   100   000    Old_age   Always       -       1148
 10 Spin_Retry_Count        0x0012   100   100   060    Old_age   Always       -       0
 12 Power_Cycle_Count       0x0032   100   100   000    Old_age   Always       -       3
 22 Unknown_Attribute       0x0023   100   100   025    Pre-fail  Always       -       100
192 Power-Off_Retract_Count 0x0032   100   100   000    Old_age   Always       -       51
193 Load_Cycle_Count        0x0012   100   100   000    Old_age   Always       -       51
194 Temperature_Celsius     0x0002   144   144   000    Old_age   Always       -       45 (Min/Max 20/54)
196 Reallocated_Event_Count 0x0032   100   100   000    Old_age   Always       -       0
197 Current_Pending_Sector  0x0022   100   100   000    Old_age   Always       -       0
198 Offline_Uncorrectable   0x0008   100   100   000    Old_age   Offline      -       0
199 UDMA_CRC_Error_Count    0x000a   200   200   000    Old_age   Always       -       0

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.

jak # 

# mdadm.conf
#
# !NB! Run update-initramfs -u after updating this file.
# !NB! This will ensure that initramfs has an uptodate copy.
#
# Please refer to mdadm.conf(5) for information about this file.
#

# by default (built-in), scan all partitions (/proc/partitions) and all
# containers for MD superblocks. alternatively, specify devices to scan, using
# wildcards if desired.
#DEVICE partitions containers

# automatically tag new arrays as belonging to the local system
HOMEHOST 

# instruct the monitoring daemon where to send mail alerts
MAILADDR root

# definitions of existing MD arrays
ARRAY /dev/md/0  metadata=1.2 UUID=7636d5d0:8c9d0823:7252c563:30724789 name=jak:0
ARRAY /dev/md130 metadata=1.2 UUID=809a185b:a2613844:3975b412:759ec297 name=jak:sour

# This configuration was auto-generated on Sat, 28 Apr 2018 16:34:38 -0700 by mkconf

Remaining question now

  • /etc/md/jak:neat and /etc/md/jak:sour do not appear. What process creates those?

  • running blkid /dev/md127 returns no output. It does return expected output against /dev/md0. Therefore, my fstab now lists the file system devices as /dev/md127 and /dev/md130 which feels temporary.

Comments appreciated in advance!

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  • I have faith in you being able to solve the remaining puzzles. If your core question has been answered, don't forget to mark it solved after 2 days. Anyway, the remaining questions seem a bit too much for this one Q & A. I'd advise to ask a new question regarding those. Cheers. Commented Oct 6, 2019 at 19:18

1 Answer 1

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1

Thanks to LinuxSecurityFreak for some clues.

I had not ever (deliberately) updated mdadm.conf (man page); I didn't know it was there. Adding the missing ARRAY has indeed helped.

Also, I had not (deliberately) run update-initramfs (man page).

Taking these two steps has made it boot my station successfully twice in a row, so that's awesome.

Please look into my remaining problems at the end of my question.

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