Data ONTAP Discussions

Viewing read only luns?

Hi, I've asked this before but didn't get all the info needed. I have two fas2020with the second filer running as my DR, I have snapmirror running on one volume which has LUNS in it. This volume is replicated to filer2, now I understand that I cannot mount the destination(replicated) LUNS as they are on the read only(destination) volume...but my client insists that he be able to see for himself that the replication is working...

So I've read that I can create a flexclone of the destination volume and mount as read/write from here.....however when running through the procedure on the destination filer I receive and error "can't create snapshot for operation"

Can anyone shed some light here or let me know the best way to mount the destination LUN?



Re: Viewing read only luns?

So you can mount the snapshot copies of the LUNS…they will be read only, but will show the client that there is copies of the appropriate data on your DR LUN.

Snapdrive is the key to doing this really…you can either remount the lun on the production servers or on another box with SD installed.

In terms of cloning…yes will be able to…when you do a clone, you can either say create new snapshot…or base it on an existing snapshot…do you get the same error with both?

But would add, just to test that the data is there…just mount a snapshot copy of the LUN and show the user the contents…if they don’t need to change it…no need to clone it…

Cloning great for DR testing… but not necessary to prove a point!

Re: Viewing read only luns?

you can always do a snapmirror break of the volume, check the lun content and then resync again. just do not delete the shared snapshot.

Re: Viewing read only luns?

Thanks PSF,

The snapdrive sounds like the business....I didn't even know this existed.

I have also now come across this which is the cause of my failure....I forgot to mention this is a volume level snapmirror.

"If your snapmirror is VSM (Volume-lavel snapmirror) , then you need to create snapshot on the source which will be replicated to the destination. In VSM, you cannot create snapshots as the dest-volume will be in read-only mode."

So I need to create a snapshot on the source first.

Re: Viewing read only luns?


So a SnapMirror is, as you’ve guessed a mirror operation and is designed for DR, SnapMirror mirrors the production data exactly to a second NetApp box and it’s that bit that’s important to remember, if it doesn’t exist in the production volume, it won’t exist in the volume mirror either (this would also be true of QTree Mirrors as well).

so your statement is true to create a snapshot in DR you need it to exist in production…however that’s not true of creating a Flexclone, by default it creates a writeable snapshot of data…so on the snapmirror destination you can create a clone based on the existing snapshot…

read this document gives you an outline of the things to consider when you clone SnapMirror destinations…but it does work and is supported.

As I said though…for what you are after…just mount a snapshot LUN to a box…and heah presto!

Paul Stringfellow

DDI:0151 221 3519

Tel: 0151 220 5552


Re: Viewing read only luns?

You can do flex lone. Run snap list on a destination mirrored volume. Pick the name of anyone snapshot in the list. At the least, you will see Base snapshot there. 

Run this cmd:

Dest>clone create clone_name -b parentvol parentsnap

For parentsnap you can supply the snap name you picked from the snap list on destvol.

On a read/write vol, If you don't supply snap name it automatically creates one during cloning. B'cos VSM is read only , you must explicitly   Provide snap name.

Re: Viewing read only luns?

Cmd is: vol clone create . Just prefix vol in that cmd. Sorry for typo, in the train.