Re: Root volume LS mirror best practices?

A few general rules of thumb to go by:

   1. Load-Sharing mirrors only ever benefit NAS volumes. SAN volumes have
   no need to be mounted into a namespace to function.
   2. Best to create ONE LS mirror on each data aggregate in the cluster.
      1. Sometimes this is nuts, like having 8 aggregates. At that point, I
      might defy the practice and maybe do one per node
      2. Looks like it has been a while since I looked at those docs. It
      does show one per node now. When!
      3. I personally have never had to utilize the LS mirror. It is tiny
      (1G per node per data SVM).
   3. It is really not needed to update the LS mirror every 5 minutes. Even
   the FlexPod guides set it to 15.
      1. You could always run a pre-script that does a "manual" snapmirror
      update-ls-set before any backup job to be safe (agreeing with
your example
      in a way)
   4. When you use the LS mirror, ONTAP defaults to **only** using the LS
   mirrors for client access.
      1. To access the RW version, I think you need to mount: svm:/.admin
      2. So, having the LS mirror on each node is actually a good thing for
      the clients. Stick with one LS mirror per node!
   5. One SVM_root can have many replicas They are managed as a single
   group. You update one, all get updated. very easy to manage.

Bottom line: stick with one LS mirror per node. It is quote easy to
setup (on the CLI, have never seen it able to be done in the GUI, of
course, I have never looked either)

--tmac

*Tim McCarthy, **Principal Consultant*

*Proud Member of the #NetAppATeam <https://twitter.com/NetAppATeam>*

*I Blog at TMACsRack <https://tmacsrack.wordpress.com/>*



On Fri, Apr 23, 2021 at 12:54 PM John Stoffel <[email protected]> wrote:

>
> Guys,
>
> We're getting ready to do a DC move, so I'm working to setup all my
> SnapMirror relationships to hopefully mirror all my data between my
> two pairs (all in one cluster right now).  The idea being that if one
> pair doesn't make the move, we have our data elsewhere.  No, we don't
> have any swing gear, the system is out of Netapp support, and we do
> have alot of spare space to mirror with.  Whew.  :-)
>
> So I found the Netapp documents on "SVM Root Volume Protection
> Express Guide" from 2016 and I've started to implement it here,
> because if the worse case happens and one pair doesn't make it through
> the move due to damage or loss or catastrophe, I need to be able to
> bring up as much data as possible, as quickly as possible.
>
>   https://library.netapp.com/ecm/ecm_download_file/ECMLP2496241
>
> I do have some questions for you all, to see what other people are
> doing, and what are current best practices and real life issues to
> watch out for.
>
> First, I did change my setup so that I mirror every 5 minutes, instead
> of hourly as given in the quick guide.  Since we use Netbackup to make
> clones of volumes to backup, that should hopefully work ok, but I
> worry that now I need to add in a:
>
>   snapmirror update-ls-set -source-vserver <vs> -source-volume rootvol
>
> after I create a new clone, to make sure that the backup server will
> see this clone volume and junction path.  Has anyone run into this
> issue and is your workaround to just do the update by hand, or do you
> just wait for the change to replicate?
>
> Second, this document recommends one LS mirror per-head in a cluster.
> With a four node cluster, this seems a little crazy, especially since
> I've never had any problems when doing failovers during upgrades in
> the past.  My main goal is to just have the mirrors on seperate
> pairs.  What do people think?  Is one rootvol and one rootvol_m1
> mirror per VServer enough?
>
> Third, if I go with just one LS mirror per-pair, I think it looks like I
> really need to make two mirrors, one for the source pair, and one for
> the opposite pair.  Which seems like a pain to manage, increases the
> number of volumes and SM relationships to manage, etc.  Since my main
> focus is NOT performance, since it's been working just fine without LS
> mirrors in the past, is just having one LS mirror good enough?
>
>
> Cheers,
> John
>
>
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