Reshape a RAID volume

RAID reshaping means changing attributes of a RAID logical volume without changing the RAID level. Some attributes that you can change include RAID layout, stripe size, and number of stripes.

Procedure

  1. Create a RAID logical volume: 
    # lvcreate --type raid5 -i 2 -L 500M -n my_lv my_vg
     
    Using default stripesize 64.00 KiB.
Rounding size 500.00 MiB (125 extents) up to stripe boundary size 504.00 MiB (126 extents).
Logical volume "my_lv" created.
  2. View the RAID logical volume: 
    # lvs -a -o +devices
     
    LV               VG    Attr       LSize   Pool   Origin Data% Meta% Move Log Cpy%Sync Convert Devices
my_lv            my_vg rwi-a-r--- 504.00m                                    100.00            my_lv_rimage_0(0),my_lv_rimage_1(0),my_lv_rimage_2(0)
[my_lv_rimage_0] my_vg iwi-aor--- 252.00m                                                      /dev/sda(1)
[my_lv_rimage_1] my_vg iwi-aor--- 252.00m                                                      /dev/sdb(1)
[my_lv_rimage_2] my_vg iwi-aor--- 252.00m                                                      /dev/sdc(1)
[my_lv_rmeta_0]  my_vg ewi-aor---   4.00m                                                      /dev/sda(0)
[my_lv_rmeta_1]  my_vg ewi-aor---   4.00m                                                      /dev/sdb(0)
[my_lv_rmeta_2]  my_vg ewi-aor---   4.00m                                                      /dev/sdc(0)
  3. Optional: View the stripes images and stripesize of the RAID logical volume: 
    # lvs -o stripes my_vg/my_lv
     
      #Str
     3
     
    # lvs -o stripesize my_vg/my_lv
     
      Stripe
  64.00k
  4. Modify the attributes of the RAID logical volume by using the following ways depending on your requirement:
    1. Modify the stripes images of the RAID logical volume: 
      # lvconvert --stripes 3 my_vg/my_lv
       
      Using default stripesize 64.00 KiB.
WARNING: Adding stripes to active logical volume my_vg/my_lv will grow it from 126 to 189 extents!
Run "lvresize -l126 my_vg/my_lv" to shrink it or use the additional capacity.
Are you sure you want to add 1 images to raid5 LV my_vg/my_lv? [y/n]: y
Logical volume my_vg/my_lv successfully converted.
    2. Modify the stripesize of the RAID logical volume: 
      # lvconvert --stripesize 128k my_vg/my_lv
       
        Converting stripesize 64.00 KiB of raid5 LV my_vg/my_lv to 128.00 KiB.
Are you sure you want to convert raid5 LV my_vg/my_lv? [y/n]: y
  Logical volume my_vg/my_lv successfully converted.
    3. Modify the maxrecoveryrate and minrecoveryrate attributes: 
      # lvchange --maxrecoveryrate 4M my_vg/my_lv
       
        Logical volume my_vg/my_lv changed.
       
      # lvchange --minrecoveryrate 1M my_vg/my_lv
       
        Logical volume my_vg/my_lv changed.
    4. Modify the syncaction attribute: 
      # lvchange --syncaction check my_vg/my_lv
    5. Modify the writemostly and writebehind attributes: 
      # lvchange --writemostly /dev/sdb my_vg/my_lv
       
        Logical volume my_vg/my_lv changed.
       
      # lvchange --writebehind 100 my_vg/my_lv
       
        Logical volume my_vg/my_lv changed.
      Note
      All operations are not supported for all volume types. Check the specific volume type requirements and limitations before proceeding.

Results

  1. View the stripes images and stripesize of the RAID logical volume: 
    # lvs -o stripes my_vg/my_lv
     
      #Str
     4
     
    # lvs -o stripesize my_vg/my_lv
     
      Stripe
  128.00k
  2. View the RAID logical volume after modifying the maxrecoveryrate attribute: 
    # lvs -a -o +raid_max_recovery_rate
     
      LV               VG       Attr        LSize   Pool Origin Data%  Meta%  Move Log Cpy%Sync Convert MaxSync
  my_lv            my_vg    rwi-a-r---  10.00g                                     100.00           4096
  [my_lv_rimage_0] my_vg    iwi-aor---  10.00g
 [...]
  3. View the RAID logical volume after modifying the minrecoveryrate attribute: 
    # lvs -a -o +raid_min_recovery_rate
     
      LV               VG     Attr        LSize   Pool Origin Data%  Meta%  Move Log Cpy%Sync Convert MinSync
  my_lv            my_vg  rwi-a-r---  10.00g                                     100.00           1024
  [my_lv_rimage_0] my_vg  iwi-aor---  10.00g
  [...]
  4. View the RAID logical volume after modifying the syncaction attribute: 
    # lvs -a
     
      LV               VG      Attr        LSize   Pool Origin Data%  Meta%  Move Log Cpy%Sync Convert
  my_lv            my_vg   rwi-a-r---  10.00g                                     2.66
  [my_lv_rimage_0] my_vg   iwi-aor---  10.00g
  [...]