3

I just bought a new disk. How do I extend an existing RAID array without losing data?

6

If you make a mistake, you can lose all your data. Backup first. Then continue.

Use storcli /c0 show to see what drives and volumes you have. The TOPOLOGY table is a good start:

TOPOLOGY :
========

----------------------------------------------------------------------------
DG Arr Row EID:Slot DID Type  State BT      Size PDC  PI SED DS3  FSpace TR 
----------------------------------------------------------------------------
 0 -   -   -        -   RAID5 Optl  N  10.914 TB dflt N  N   none N      N  
 0 0   -   -        -   RAID5 Optl  N  10.914 TB dflt N  N   none N      N  
 0 0   0   252:0    10  DRIVE Onln  N   2.728 TB dflt N  N   none -      N  
 0 0   1   252:1    9   DRIVE Onln  N   2.728 TB dflt N  N   none -      N  
 0 0   2   252:2    11  DRIVE Onln  N   2.728 TB dflt N  N   none -      N  
 0 0   3   252:3    8   DRIVE Onln  N   2.728 TB dflt N  N   none -      N  
 0 0   4   252:4    12  DRIVE Onln  N   2.728 TB dflt N  N   none -      N  
----------------------------------------------------------------------------

This shows you which disks are already in the RAID array. I only have a single RAID array (Arr) with the ID 0.

PD LIST shows you the disks:

PD LIST :
=======

--------------------------------------------------------------------------------
EID:Slt DID State DG     Size Intf Med SED PI SeSz Model                Sp Type 
--------------------------------------------------------------------------------
252:0    10 Onln   0 2.728 TB SATA HDD N   N  512B WDC WD30EFRX-68AX9N0 U  -    
252:1     9 Onln   0 2.728 TB SATA HDD N   N  512B WDC WD30EFRX-68AX9N0 U  -    
252:2    11 Onln   0 2.728 TB SATA HDD N   N  512B WDC WD30EFRX-68EUZN0 U  -    
252:3     8 Onln   0 2.728 TB SATA HDD N   N  512B WDC WD30EFRX-68EUZN0 U  -    
252:4    12 Onln   0 2.728 TB SATA HDD N   N  512B WDC WD30EFRX-68EUZN0 U  -    
252:6    14 GHS    - 2.728 TB SATA HDD N   N  512B WDC WD30EFRX-68EUZN0 D  -    
252:7    13 UGood  - 2.728 TB SATA HDD N   N  512B WDC WD30EFRX-68EUZN0 D  -    
--------------------------------------------------------------------------------

The newly added disk should show up as UGood (unconfigured good). In the example, that's the disk 13 in slot 7 of enclosure 252.

To add the disk to the RAID array:

storcli /c0/v0 start migrate type=raid5 option=add drives=252:13

/c0 is the controller, /v0 is the RAID volume (see TOPOLOGY above or VD LIST) to change, start migrate is the command to issue, type=raid5 means "keep it RAID5", we want to add a disk (option=add) and drives is the list of disks to add in the form EID:Slt (see PD LIST).

The process can take several days. You can continue to use the file system(s) on the RAID volume while the controller does the work in the background. You can even reboot the server, the controller will just continue from where it was.

To check the progress, use storcli /c0/v0 show migrate which will print something like:

VD Operation Status :
===================

-----------------------------------------------------------
VD Operation Progress% Status          Estimated Time Left 
-----------------------------------------------------------
 0 Migrate          38 In Progress     49 Minutes                   
-----------------------------------------------------------

Note: The estimation is way off; those 49 minutes were 3 hours in my case. My feeling is that that first estimation of 2 days 8 hours was way more accurate.

When the migration is finished, the controller will do another background job ("background initialization"). Not sure what that is.

When it's done, it will print:

VD Operation Status :
===================

-----------------------------------------------------------
VD Operation Progress% Status          Estimated Time Left 
-----------------------------------------------------------
 0 Migrate   -         Not in progress -                   
-----------------------------------------------------------

Use storcli /c0 show to see the new size of your RAID volume:

VD LIST :
=======

--------------------------------------------------------------
DG/VD TYPE  State Access Consist Cache Cac sCC      Size Name 
--------------------------------------------------------------
0/0   RAID5 Optl  RW     Yes     RWBD  -   OFF 10.914 TB data 
--------------------------------------------------------------
                                               ^^^^^^

I'm using LVM to manage the disk. pvscan shows that the disk size hasn't changed:

PV /dev/sdb   VG data   lvm2 [8,19 TiB / 526,00 GiB free]
                              ^^^^^^^^

Time to reboot (at least I couldn't find a way to make Linux rescan the disk).

At least, lsblk now shows the correct disk size:

sdb              8:16   0  10,9T  0 disk
                           ^^^^^

LVM still can't see it (pvscan):

PV /dev/sdb   VG data   lvm2 [8,19 TiB / 526,00 GiB free]

pvdisplay gives more details:

  --- Physical volume ---
  PV Name               /dev/sdb
  VG Name               data
  PV Size               8,19 TiB / not usable 3,00 MiB
  Allocatable           yes 
  PE Size               4,00 MiB
  Total PE              2145791
  Free PE               134655
  Allocated PE          2011136
  PV UUID               vM1WQP-CZXu-FrWJ-kRti-hMa2-I1rh-Mga6Xg

We can test the next operation before executing it: pvresize --test -v /dev/sdb

  TEST MODE: Metadata will NOT be updated and volumes will not be (de)activated.
    Using physical volume(s) on command line.
    Test mode: Skipping archiving of volume group.
    Resizing volume "/dev/sdb" to 23437770752 sectors.
    Resizing physical volume /dev/sdb from 0 to 2861055 extents.
    Updating physical volume "/dev/sdb"
    Test mode: Skipping backup of volume group.
  Physical volume "/dev/sdb" changed
  1 physical volume(s) resized / 0 physical volume(s) not resized
    Test mode: Wiping internal cache
    Wiping internal VG cache

2861055 extents a 4 MiB translates to 10.91 TiB (2861055*4096/1024/1024/1024).

Resize the logical volume: pvresize -v /dev/sdb

Finally, LVM sees the new capacity:

# pvdisplay 
  --- Physical volume ---
  PV Name               /dev/sdb
  VG Name               data
  PV Size               10,91 TiB / not usable 3,00 MiB
  Allocatable           yes 
  PE Size               4,00 MiB
  Total PE              2861055
  Free PE               849919
  Allocated PE          2011136
  PV UUID               vM1WQP-CZXu-FrWJ-kRti-hMa2-I1rh-Mga6Xg

You can now continue to grow the file systems on the volume group.

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