Snapmirror - can it be deleted

Posted on 2012-09-06
Last Modified: 2012-09-12
Dear Netapp and Storage experts.

I have a requirement to delete some snapshots from a Netapp filer including the first of two snapmirrors. This is where I stumbled upon, since I am wondering why there exist two snapmirror and what role resp. functionality they have.

Thus I have some questions:

1. How can there be two snapmirrors
2. Can the first snapmirror be deleted
3. What happens to once I deleted this snapmirror. Do I invalidate the second snapmirror and all snapshots above the first snapmirror as well?
4. Are Snapmirrors always indicators that the Snapshots are saved on Nearstores?

From my knowledge I compare these Snapmirrors to incremental RMAN backups.
The Snapmirror is the base (level 0) backup that contains all datafiles. All other Snapshots are what is known in RMAN as level 1 incremental backups. I Netapp terms they just point to the changed blocks within the snapmirror. Hence if I delete the lower snapmirror, all other snapshots above are invalidated and can be deleted as well.

If you could clarify my questions I'd appreciate it very much.

Here's an example of my snapshot list:

Aug 29 19:17  ORASID_02052012_SNAPSHOT_20121030
Aug 29 13:51  ORASID_02052012_SNAPSHOT_201221030
Aug 28 20:46  ORASID_30042012_SNAPSHOT_20121030
Aug 20 10:50  ORASID_30042012_SNAPSHOT_201221030
Aug 17 15:36  ORASID_27042012_SNAPSHOT_20121030 (Snapmirror)
Aug 17 11:53  ORASID_27042012_SNAPSHOT_201221030
Aug 16 17:25  ORASID_16042012_SNAPSHOT_20121030
Aug 16 13:46  ORASID_16042012_SNAPSHOT_201221030
Aug 15 17:40  ORASID_11042012_SNAPSHOT_20121030 <== Delete until here
Aug 15 12:52  ORASID_11042012_SNAPSHOT_201221030 (Snapmirror)
Aug 14 19:35  ORASID_30032012_SNAPSHOT_20121030
Aug 14 12:01  ORASID_30032012_SNAPSHOT_20121030
Aug 13 16:09  ORASID_29032012_SNAPSHOT_201221030 <== Start deletion
Question by:skahlert2010
    LVL 21

    Accepted Solution

    Use the command "snapmirror status" to see the actual snapmirror relationships.
    Could you post the output here, it makes it easier to discuss your situation.

    1. 2 snapmirror relations to different destinations ?
    2. Snapshots that are actively being used by the snapmirror relation are protected against deletion
    3. see 2
    4. what you see in your list are snapshots, not the snapmirror relations. Use snapmirror status to see what is actually going on.

    Snapmirror is "incremental forever". The snapmirror snapshot does indeed keep the changes since the last transfer. After transfer, a new snapshot is taken that is the new baseline for the next transfer. The snapmirror snapshots are protected to prevent the snapmirror relation from being invalidated.

    Author Comment

    Hi robocat!

    Thank you explanation.

    I executed the "snapmirror status" command and received the following output concerning my database and volume.

    Snapmirror Source: wersg031:/vol/wersg031_v999/ORADATA01_MYSID
    is Destination: wersgb17:/vol/sm_wersg031_v999/ORADATA01_MYSID      
    on State: Source
    Lag: 363:06:18      
    Status: Idle

    In fact I could only detect 1 snapmirror relation using that command.
    However, the snapshot list still shows me 2 snapmirror relations.

    Is there a way to see the snapshots and their relation to the snapmirrors at once?

    Sorry for the question but as a total netapp newbie, this is quite some hard stuff.

    Thanks for your help!
    LVL 21

    Expert Comment

    You're absolutely sure there's no other snapmirror relations for the same source volume in the list ?

    The snapmirror hasn't been updated for 363 hours, so you  should probably do that first. It may make things a bit clearer.

    See which snapshots remain designated as "snapmirror" afterwards.
    LVL 42

    Expert Comment

    Are you running protection manager?  Snapmirror relationships can be initiaged from multiple locations.

    On the filer type "rdfile /etc/snapmirror.conf" this is actually where the snapmirror relationships are defined (this would be on your destination filer)

    If you see multiple entries in there then the relationships still exist.

    I have also seen relationships still show up until destination volumes were deleted even though there was no replication taking place.

    Author Comment

    Hi robocat and paulsolov!

    Thanks a lot for replying!


    I will check it again tomorrow as I don't have access to the system right now.
    But basically, yes I am sure that there are no other snapmirror relations.


    I am not sure if the protection manager is used or not.
    You need to know that the storage is outsourced and I have limited access to the system.
    All I can do is login remote and execute some statements in the shell.
    I have no idea how the setup looks like.

    The problem is that I need to tell the second level support which snapshots to delete. Hence I need to know about the structure and the relations of the snapmirrors to avoid corruption of the database backups.
    LVL 42

    Assisted Solution

    Check the snapmirror.conf file and see if it has a cron schedule, if so then it's being kicked off by the netapp controller most likely, if it doesn't than most likely by protection manager.  Youc an also check the /etc/messages to see if there is any connections from a different IP that could be kicking off the job

    Author Comment

    Hi paulsolov!

    I just tried to read the snapmirror.conf but unfortunately permission is denied.
    I assume that the protection manager is used instead of cron. Executing snapmirror status I found 69 snapmirrors and actually believe that handling these by cron is too much of a hazard.

    I made a request for clarification and hope the storage and backup department, who host our backups will reply today. It is really helpful to learn from you but it's probably best to know from the system owners what is going on.

    I will keep you updated and close the thread once the question is resolved, okay?

    Thanks for your effort!
    LVL 21

    Expert Comment

    At the time you started your question (Sep 06), the snapmirror had not run since Aug 15 or Aug 17.

    That's a really long time for being without backups by any standard. Perhaps you should ask some hard questions to the storage & backup department.

    Any backups managed by Protection Manager or Snapmanager for Oracle should be regularly monitored. Otherwise you could find that there are no recent backups at the moment you really need it.

    BTW: snapmirror can leave busy snapshots when something goes wrong. Perhaps this is the reason why you see 2 busy snapshots and no backups since Aug 17.
    LVL 42

    Expert Comment

    @robocot: Unless someone clicked "initialize" and they're re-seeding the volumes..I have see that before..customer clicked initialize instead of resync.

    Author Closing Comment

    Thanks guys!<br /><br />The two snapmirrors I saw where simply due to the snaplist showing entries not properly. Using your hints such as snapmirror config, I was able to find out that there's indeed only one snapmirror and actually deleted the one in doubt. Furthermore I learned a little mor e about that netapp topic and appreciate your help.<br /><br />There are still a bunch of questions that remain but it'll be best to ask them in a separate thread.<br /><br />Thank you!!!

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