Sunday, 29 May 2016

Moving Volumes Between SVMs post Transition

Note 1: Version of cDOT is 8.3.2 GA.
Note 2: Version of 7MTT is 2.3.1.

NetApp Library covers this very well in the following article:

There was something I wanted to see though (to be revealed - and I wanted to have a play anyway) hence I ran it though a simple lab.

Lab Setup

We have a 7-Mode system called FAS101.
We are going to create a volume called VOL001 that we want to transition to cDOT.
The 7-Mode volume is going to be transitioned to cDOT cluster clu1, and SVM1.
Post transition we’ll rehost the volume to SVM2.

SVM1 and SVM2 already exist, and transitions have already been carried out from FAS101 to SVM1, so all we need to do is create a test volume with some test data, and transition it:

On FAS101>


vol create VOL001 -l en -s none aggr0 2g
cifs shares -add VOL001 /vol/VOL001


Using 7MTT CLI>


transition credentials add -h 10.0.1.50 -u root
transition credentials add -h 10.0.1.100 -u admin
transition create -s SESSION1 -t standalone -n 10.0.1.50 -c 10.0.1.50 -h 10.0.1.100 -v SVM1
transition volumepair add -s SESSION1 -v VOL001 -c VOL001 -g clu1n2_sata_aggr1
transition schedule add -s SESSION1 -n SCHED1 -d 0-6 -b 00:00 -e 24:00 -t 25 -u 16:00
transition show -s SESSION1 -r no
transition precheck -s SESSION1 -r no
transition start -s SESSION1 -n -r no
transition precutover -s SESSION1 -m no_test -r no
transition cutover -s SESSION1 -r no


Re-Hosting the Volume - Full Output

Note: Since this was a NAS volume, I need to unmount first, otherwise the rehost will fail.

On clu1::>


set advanced
volume unmount -volume VOL001 -vserver SVM1
volume rehost -vserver SVM1 -volume VOL001 -destination-vserver SVM2

Warning: Rehosting a volume from one Vserver to another Vserver does not change the security information on that volume. If the security domains of the Vservers are not identical, unwanted access might be permitted, and desired access might be denied. An attempt to rehost a volume will disassociate the volume from all volume policies and policy rules. The volume must be reconfigured after a successful or unsuccessful rehost operation. See the "7-Mode Transition Tool 2.2 Copy-Free Transition Guide" for reconfiguration details.
Do you want to continue? y
[Job 124] Job succeeded: Successful

Info: Volume is successfully rehosted on the target Vserver.
Set the desired volume configuration - such as the export policy and QoS policy - on the target Vserver.


What I was Looking For

I hadn’t shown myself running the below in diag mode -


::> vol show -volume VOL001 -instance


- before and after the rehost operation. I was looking to see if any of these details changed post rehost (basically anything with the word “transition” in):

Transition Operation State: none
Transition Behaviour: none
Copied for Transition: true
Transition: true

The answer is that nothing changed; which got me to thinking...

Q: Can I move the volume back again? YES


volume rehost -vserver SVM2 -volume VOL001 -destination-vserver SVM1


Q: Can I move it to another SVM (say I picked the wrong SVM in the first place)? YES


volume rehost -vserver SVM1 -volume VOL001 -destination-vserver SVM2
volume rehost -vserver SVM2 -volume VOL001 -destination-vserver clu1-svm1


Q: Can I rehost transitioned volumes ad inifinitum? No idea - I’ll have to ask someone.

4 comments:

  1. Unfortunately, this only works for transitioned volumes. You cannot rehost volumes which were created on cDOT to a different SVM:

    cluster832::*> vol rehost -vserver svm1 -volume svm1_vol1 -destination-vserver svm2

    Error: command failed: Cannot rehost volume "svm1_vol1" on Vserver "svm1" because volume is not a transitioned volume.

    ReplyDelete
  2. I believe the restriction of a Cluster Admin only being able to move transitioned volumes between SVMs - and not just any volume - is going to be lifted in a future release...

    ReplyDelete
  3. So I tried this on 9.1RC1 and it seems to work for a regular volume created on CDOT.

    ::*> vol create -vserver SVM1 -volume move_vol_crtd_cdot -aggregate aggr1 -size 2g -state online
    [Job 4658] Job succeeded: Successful

    ::*> vol rehost -vserver SVM1-volume move_vol_crtd_cdot -destination-vserver SVM2

    Warning: Rehosting a volume from one Vserver to another Vserver does not change the security information on that volume.
    If the security domains of the Vservers are not identical, unwanted access might be permitted, and desired access might be denied. An attempt to rehost a volume will
    disassociate the volume from all volume policies and policy rules. The volume must be reconfigured after a successful or unsuccessful rehost operation.
    Do you want to continue? {y|n}: y
    [Job 4659] Job succeeded: Successful

    Info: Volume is successfully rehosted on the target Vserver.
    Set the desired volume configuration - such as the export policy and QoS policy - on the target Vserver.

    ReplyDelete
    Replies
    1. Thanks unknown. I believe they removed the restriction on only being able to rehost transitioned volumes in ONTAP 9.0.

      Delete