0

i have a raspberry pi with two USB thumb drives that are in a mirror raid array and store my data that I share using Nextcloud. Now randomly, I caught today that one USB drive LED was flashing without any obvous reason so I connected to my pi and did cat /proc/mdstat and what I saw was:

$ cat /proc/mdstat 
Personalities : [raid1] 
md0 : active raid1 sdb1[1] sda1[2]
      120109056 blocks super 1.2 [2/2] [UU]
      [===================>.]  check = 99.9% (120103296/120109056) finish=0.0min speed=18842K/sec
      bitmap: 0/1 pages [0KB], 65536KB chunk

I was awatching it just before it reached 99.9% but this is the laast resync message I caught, after this it looks like:

$ cat /proc/mdstat 
Personalities : [raid1] 
md0 : active raid1 sdb1[1] sda1[2]
      120109056 blocks super 1.2 [2/2] [UU]
  bitmap: 0/1 pages [0KB], 65536KB chunk

Now, how do I find out why the resync happened and if one of the drives is actually bad and should be replaced? sda1 andsdb1still looks good withlsblk`:

$ lsblk
NAME        MAJ:MIN RM   SIZE RO TYPE  MOUNTPOINT
sda           8:0    1 119.3G  0 disk  
└─sda1        8:1    1 114.6G  0 part  
  └─md0       9:0    0 114.6G  0 raid1 /mnt/usb
sdb           8:16   1 114.6G  0 disk  
└─sdb1        8:17   1 114.6G  0 part  
  └─md0       9:0    0 114.6G  0 raid1 /mnt/usb
mmcblk0     179:0    0  29.2G  0 disk  
├─mmcblk0p1 179:1    0   256M  0 part  /boot
└─mmcblk0p2 179:2    0    29G  0 part  /

UPDATE:

There's no /etc/charray but /etc/cron.d/mdadm looks like:

$ cat /etc/cron.d/mdadm 
#
# cron.d/mdadm -- schedules periodic redundancy checks of MD devices
#
# Copyright © martin f. krafft <madduck@madduck.net>
# distributed under the terms of the Artistic Licence 2.0
#

# By default, run at 00:57 on every Sunday, but do nothing unless the day of
# the month is less than or equal to 7. Thus, only run on the first Sunday of
# each month. crontab(5) sucks, unfortunately, in this regard; therefore this
# hack (see #380425).
57 0 * * 0 root if [ -x /usr/share/mdadm/checkarray ] && [ $(date +\%d) -le 7 ]; then /usr/share/mdadm/checkarray --cron --all --idle --quiet; fi

which refers to /usr/share/mdadm/checkarray which is a script that doesn't produce ant output to stdout when it is run.

2
  • 1
    Do you have an /etc/cron.d/checkarray or /etc/cron.d/mdadm file, and if so what is in it? – icarus May 3 '20 at 3:46
  • 1
    probably just a periodic check but you can see if there were any errors in dmesg – frostschutz May 3 '20 at 15:28
2

There is a cron job run in the early hours of the morning of the first sunday of the month which does a full check of the array. The OP caught it running.

2
  • Okay, nothing to worry about then? It wasn't Sunday early hours in my time zone but for UTC, that is about true! – stdcerr May 3 '20 at 18:37
  • 1
    Almost certainly nothing to worry about. – icarus May 3 '20 at 21:42

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.