What is this phantom RAID array

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brimur
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What is this phantom RAID array

Postby brimur » Wed Oct 18, 2017 6:27 pm

Hi guys,

I have a DS1815+ 8-bay NAS. I am using bays 1 and 2 as a RAID 1 SSD cache and bays 3 - 8 as a 6 disk RAID5/SHR array

I was just looking at the output of

Code: Select all

sh-4.3# cat /proc/mdstat
and I see the 2 disk RAID1 md4 cache array and the 6 disk RAID5/SHR array md2 but I am also seeing a 4 disk RAID5 array called md3 and I am wondering what it is?

Code: Select all

sh-4.3# cat /proc/mdstat
Personalities : [linear] [raid0] [raid1] [raid10] [raid6] [raid5] [raid4]
md2 : active raid5 sdf5[6] sdh5[8] sdg5[9] sdc5[3] sde5[2] sdd5[7]
      14627177280 blocks super 1.2 level 5, 64k chunk, algorithm 2 [6/6] [UUUUUU]

md3 : active raid5 sdf6[5] sdg6[4] sdh6[3] sdd6[1]
      14651252736 blocks super 1.2 level 5, 64k chunk, algorithm 2 [4/4] [UUUU]

md4 : active raid1 sda1[0] sdb1[1]
      732569984 blocks super 1.2 [2/2] [UU]

md1 : active raid1 sdc2[5] sdd2[1] sde2[4] sdf2[0] sdg2[3] sdh2[2]
      2097088 blocks [8/6] [UUUUUU__]

md0 : active raid1 sdc1[3] sdd1[1] sde1[2] sdf1[0] sdg1[4] sdh1[5]
      2490176 blocks [8/6] [UUUUUU__]

unused devices: <none>
sh-4.3# mdadm --detail /dev/md2
/dev/md2:
        Version : 1.2
  Creation Time : Thu Dec 22 16:41:08 2016
     Raid Level : raid5
     Array Size : 14627177280 (13949.56 GiB 14978.23 GB)
  Used Dev Size : 2925435456 (2789.91 GiB 2995.65 GB)
   Raid Devices : 6
  Total Devices : 6
    Persistence : Superblock is persistent

    Update Time : Wed Oct 18 18:14:57 2017
          State : active
 Active Devices : 6
Working Devices : 6
 Failed Devices : 0
  Spare Devices : 0

         Layout : left-symmetric
     Chunk Size : 64K

           Name : Nas:2  (local to host Nas)
           UUID : fbc07ead:56e8e9ef:6ea89a6f:c892e2e7
         Events : 603680

    Number   Major   Minor   RaidDevice State
       6       8       85        0      active sync   /dev/sdf5
       7       8       53        1      active sync   /dev/sdd5
       2       8       69        2      active sync   /dev/sde5
       3       8       37        3      active sync   /dev/sdc5
       9       8      101        4      active sync   /dev/sdg5
       8       8      117        5      active sync   /dev/sdh5
sh-4.3# mdadm --detail /dev/md3
/dev/md3:
        Version : 1.2
  Creation Time : Tue Jan  3 19:47:04 2017
     Raid Level : raid5
     Array Size : 14651252736 (13972.52 GiB 15002.88 GB)
  Used Dev Size : 4883750912 (4657.51 GiB 5000.96 GB)
   Raid Devices : 4
  Total Devices : 4
    Persistence : Superblock is persistent

    Update Time : Wed Oct 18 18:14:43 2017
          State : clean
 Active Devices : 4
Working Devices : 4
 Failed Devices : 0
  Spare Devices : 0

         Layout : left-symmetric
     Chunk Size : 64K

           Name : Nas:3  (local to host Nas)
           UUID : eecf85ac:5a35be87:666e3853:b9e170a1
         Events : 113559

    Number   Major   Minor   RaidDevice State
       5       8       86        0      active sync   /dev/sdf6
       1       8       54        1      active sync   /dev/sdd6
       3       8      118        2      active sync   /dev/sdh6
       4       8      102        3      active sync   /dev/sdg6
sh-4.3#

DiskStation: 413j,1815+
DSM 6.1.3-15152 Update 2
sincarne
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Re: What is this phantom RAID array

Postby sincarne » Wed Oct 18, 2017 9:40 pm

different size disk?
brimur
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Re: What is this phantom RAID array

Postby brimur » Wed Oct 18, 2017 11:39 pm

There are different size disks in the array, does it group similar size disks as a separate array?
DiskStation: 413j,1815+
DSM 6.1.3-15152 Update 2
v_mark
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Re: What is this phantom RAID array

Postby v_mark » Wed Nov 08, 2017 11:23 pm

In a RAID array the partition sizes should be the same (or at least it is waste not to have).
@sincarne suspects that system made same partitions (biggest available in the smallest hard drive, in this case sdc and sde) and made another raid from the extra space of your sdd sdf sdg sdh.

I am curious how to eliminate md1 - which is a swap partition and I really do not want to software raid it:
- I stopped (mdadm --stop /dev/md1)
- I deleted (mdadm --remove /dev/md1)
- I cleared (mdadm --zero-superblock /dev/sdb2)
- I formatted (mkswap -L swap /dev/sdb2)
- I activated (swapon /dev/sdb2)
- I wrote in /etc/fstab (new line: /dev/sdb2 none swap defaults 0 0)

...after reboot, everything lost:
- md1 is working
- /etc/fstab was overwritten
Ps: currently I have only 1 drive in my 2 bay DS216j (as sdb).

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