# mdadm

Some tips and tricks regarding `mdadm`.

## raid 6 ioperf tests

### 4k random read write tests

```

fio --name TEST --filename=temp.file --rw=randrw --size=4g --io_size=10g --blocksize=4k --ioengine=libaio --fsync=1 --iodepth=1 --direct=1 --numjobs=16 --runtime=60

Run status group 0 (all jobs):

   READ: bw=489KiB/s (500kB/s), 28.9KiB/s-32.5KiB/s (29.5kB/s-33.2kB/s), io=28.7MiB (30.1MB), run=60002-60062msec

  WRITE: bw=499KiB/s (511kB/s), 29.4KiB/s-33.2KiB/s (30.1kB/s-33.0kB/s), io=29.3MiB (30.7MB), run=60002-60062msec

```

### 128k random read write tests

```

fio --name TEST --filename=temp.file --rw=randrw --size=4g --io_size=10g --blocksize=128k --ioengine=libaio --fsync=1 --iodepth=1 --direct=1 --numjobs=16 --runtime=60

Run status group 0 (all jobs):

   READ: bw=16.5MiB/s (17.2MB/s), 1007KiB/s-1107KiB/s (1031kB/s-1133kB/s), io=988MiB (1036MB), run=60003-60043msec

  WRITE: bw=16.7MiB/s (17.6MB/s), 1017KiB/s-1126KiB/s (1042kB/s-1153kB/s), io=1005MiB (1054MB), run=60003-60043msec

```

### 4M random read write tests

```

fio --name TEST --filename=temp.file --rw=randrw --size=4g --io_size=10g --blocksize=4M --ioengine=libaio --fsync=1 --iodepth=1 --direct=1 --numjobs=16 --runtime=60 

Run status group 0 (all jobs):

   READ: bw=208MiB/s (218MB/s), 11.9MiB/s-14.1MiB/s (12.5MB/s-14.7MB/s), io=12.2GiB (13.1GB), run=60011-60081msec

  WRITE: bw=205MiB/s (215MB/s), 11.9MiB/s-13.8MiB/s (12.4MB/s-14.5MB/s), io=12.1GiB (12.9GB), run=60011-60081msec

```

## Reconfigure to raid10

We have 14 free disks to be used, so let's create raid 10 array with 10 disk and 4 four as `spare` devices for auto-rebuild in case of failure

```

mdadm -v --create /dev/md0 --level=raid10 --layout=f2 --raid-devices=10 /dev/sdc /dev/sdd /dev/sde /dev/sdf /dev/sdg /dev/sdh /dev/sdi /dev/sdj /dev/sdk /dev/sdl

 mdadm --detail /dev/md0

/dev/md0:

           Version : 1.2

     Creation Time : Tue Jun 22 12:20:31 2021

        Raid Level : raid10

        Array Size : 48831523840 (45.48 TiB 50.00 TB)

     Used Dev Size : 9766304768 (9.10 TiB 10.00 TB)

      Raid Devices : 10

     Total Devices : 10

       Persistence : Superblock is persistent

     Intent Bitmap : Internal

       Update Time : Tue Jun 22 12:20:58 2021

             State : clean, resyncing 

    Active Devices : 10

   Working Devices : 10

    Failed Devices : 0

     Spare Devices : 0

            Layout : far=2

        Chunk Size : 512K

Consistency Policy : bitmap

     Resync Status : 0% complete

              Name : storage02.rdu2.centos.org:0  (local to host storage02.rdu2.centos.org)

              UUID : 521a6cbb:cb76e0c1:dc7fe98c:fe1b0bec

            Events : 5

    Number   Major   Minor   RaidDevice State

       0       8       32        0      active sync   /dev/sdc

       1       8       48        1      active sync   /dev/sdd

       2       8       64        2      active sync   /dev/sde

       3       8       80        3      active sync   /dev/sdf

       4       8       96        4      active sync   /dev/sdg

       5       8      112        5      active sync   /dev/sdh

       6       8      128        6      active sync   /dev/sdi

       7       8      144        7      active sync   /dev/sdj

       8       8      160        8      active sync   /dev/sdk

       9       8      176        9      active sync   /dev/sdl

```

Let's increase the raid array speed

```

md_device=md0

echo max > /sys/block/${md_device}/md/sync_max

echo 500000 > /sys/block/${md_device}/md/sync_speed_min

echo 500000 > /proc/sys/dev/raid/speed_limit_max

```

### Adding other disks as Spare disks in array

```

 for i in m n o p ; do mdadm --add /dev/md0 /dev/sd${i} ; done

mdadm: added /dev/sdm

mdadm: added /dev/sdn

mdadm: added /dev/sdo

mdadm: added /dev/sdp

mdadm --detail /dev/md0|grep Devices

      Raid Devices : 10

     Total Devices : 14

    Active Devices : 10

   Working Devices : 14

    Failed Devices : 0

     Spare Devices : 4

```

### VolumeGroup create and LV/filesystem

Let's now create a vg_array volume on top of new /dev/md0 raid10 device :-1: 

```

pvcreate /dev/md0

vgcreate vg_array /dev/md0

```

## raid10 ioperf tests

```

```