How snapmirror Works in Netapp

Snapmirror in Netapp

SnapMirror feature of Data ONTAP to copy data from specified volumes or qtrees to other volumes or qtrees and how to access and use the online copied data

SnapMirror feature enables an administrator to mirror snapshot images either asynchronously or synchronously.

Asynchronous:
SnapMirror replicates snapshot images from a source volume or qtree to a partner destination volume or qtree, thus replicating source object data on destination objects at regular intervals

Synchronous
SnapMirror replicates snapshot images from a source volume to a partner destination volume at the same time it is written to the source volume.

Resons for Accessing destination Voulme:

Provide users quick access to mirrored data in the event of a disaster that
makes the source volume or qtree unavailable.
◆ Update the source to recover from disaster, data corruption (qtrees only), or
user error
◆ Archive the data to tape
◆ Balance resource loads
◆ Back up or distribute the data to remote sites

Component of Snapmirror:

Source volumes or qtrees: SnapMirror source volumes and qtrees are
writable data objects whose data is to be replicated. The source volumes and
qtrees are the objects normally visible, accessible, and writable by the storage
system clients.

Destination volumes or qtrees: The SnapMirror destination volumes and
qtrees are read-only objects, usually on a separate system, to which the source
volumes and qtrees are replicated. The destination volumes and qtrees are
SnapMirror overview
normally accessed by users only when a disaster takes down the source volumes
or qtrees and the administrator uses SnapMirror commands to make the
replicated data at the destination accessible and writable.

SnapMirror feature

1. Creates a snapshot of the data on the source volume or qtree
2. Copies it to the destination, a read-only volume or qtree
3. Updates the destination to reflect incremental changes on the source, on the
schedule you specify

Enable Snapmirror on source and destination filer


License add

source-filer> options snapmirror.enable
snapmirror.enable on
source-filer>
source-filer> options snapmirror.access
snapmirror.access legacy
source-filer>

Specifying destination systems on the source
/etc/snapmirror.allow

Source system enter the command

options snapmirror.access access_specification

source filer>options snapmirror.access host=systemA

or add ipaddress or fully qualified hostname into /etc/snapmirror.allow

configure SnapMirror to resolve host names to their IP addresses

sourcefiler>options snapmirror.checkip.enable on

Defining source and destination through /etc/snapmirror.conf

The /etc/snapmirror.conf file defines the relationship between the source and the
destination, the schedule used by the destination to copy data

Syntex:

src_system:/vol/src_vol/[src_qtree]
dest_system:/vol/dest_vol[/dest_qtree] [arguments] [sched]

EX:

sourcefiler:/vol/vol8/weiso destinationfiler:/vol/bl_vol8/weiso restart=always 0 22 * *

always -> Restart mode that SnapMirror uses to continue an incremental transfer from a checkpoint if it is interrupted.

schedule:
0 -> minute o to 59
22 -> hour can be 0 to 23
* -> day of month can be 1 to 31
* -> day of week can be 0 to 6

Initializing a SnapMirror destination


Syntex:
snapmirror initialize [options] [dest_system:]
{dest_volume | qtree_path}

EX:

Systemb>snapmirror initialize -S systemA:/vol/vol1/qtree4
systemB:/vol/vol1/qtree4bak