SnapMirror to tape without Backup software

[igor_karasik]

Newbie question:

Is any way to do SnapMirror to tape without Backup software ?

We use CA ArcServe which doesn't support SnapMirror to tape.

We currently use NDMP, but want to check if SnapMirror have better performance

Thanks !

[shubhada]

Hi,

SnapMirror to tape is possible using snapmirror store command on source and snapmirror retrieve on destination volume.

These functions are not valid for Qtrees in a SnapMirror relationship.

SnapMirror has limitations when used as a backup method.Some of them :

1.Disk geometry : If the tape is retrieved into a file system that doesn't match the optimized geometry,(by default source filesystem geometry),the retrieve can be extremely slow to the point of being unusable

2.File System Version :the destination of SnapMirror retrieve must be the same or a newer version of ONTAP than source.SnapMirror retrieve attempted on an older version of ONTAP from a newer version SnapMirror store will not succeed.

3.Snapshot issues :Since snapmirror store is used to initialize mirrors for snapmirror, it leaves snapshots around to allow the future mirror relationships to perform updates. Using SnapMirror store as a backup means that these snapshots will be left for the future updates of the mirrors. If those updates are not expected, those snapshots should be managed by another means as to not collect and use up snapshot and data resources.

4.Volume Types : The file system format is different between flexible volumes and traditional volumes which means that a snapmirror store of a flexible volume cannot be retrieved on a traditional volume and vice versa.

5.Not Archival : SnapMirror to tape backups are in a format that would only be readable by ONTAP and the WAFL file system.

6.Susceptible to bad tapes : will not have a complete picture/file system until all of the pieces are placed in the proper place. Since an incomplete file system is not usable in any way, if a tape was unusable on the destination side, the file system would not be constructible and all of the data would be unavailable.

7.Lack of Backup features : Because of its intended purpose, SnapMirror to tape does not have features that other backup software may have. Individual file restores, backup indexing and incremental backups (among other things) are not supported.

Hope this helps.

-Shubhada

[igor_karasik]

Thanks for the great answer !

Can you advise which command we need to run on Filer in order to do SM2T ?

[shubhada · Accepted solution]

At the source filer :

snapmirror store source_volume dest_tapedevices

g dest_disk_geom applies if the disk geometry of the destination

volume,is different from the disk geometry of the source volume. If they are different, use the -g parameter to

specify the destination volume disk geometry, for example:

-g 140000x10,7000x10

source_volume is the volume you are copying.

dest_tapedevices is a comma-separated list of tape devices to which you are copying the volume.

Result: SnapMirror starts transferring data to tape. This command creates a baseline transfer. If you have to use more than one tape,SnapMirror prompts you for another tape.

If SnapMirror prompts you for another tape, add another tape to the

drive, and continue transfer of data to tape by entering the following

command:

snapmirror use dest_tapedevices tape_drive

dest_tapedevices is the tape device or a comma-separated list of tape

devices to which you are copying the volume.

tape_drive is the drive holding the new tape you supplied.

To initialise Snapmirror destination via local tape :

1.Create volume on destination filer.Put the volume into restricted state.

2.Load the tape (made with snapmirror store) into the destination filer's local tape device.

3.use the command:

snapmirror retrieve dest_volume tape_drive

dest_volume is the volume that you are initializing.

tape_drive is a tape device or a comma-separated list of devices from

which you are restoring the volume.

Result: SnapMirror starts transferring data from the tape.

4.If Data ONTAP prompts you for another tape, add the next tape to

the drive and restart the initialization by entering the following

command:

snapmirror use volume tape_list

volume is the volume to which you are restoring.

tape_list is the tape device from which you are restoring the volume.

-Shubhada