Data Migration -- Estimating Time lines

[vreddypalli]

Hi,

We have a situation to copy 2.5TB of Data from exiting Disk shelfs to another shelf.  Now we want to ask for the downtime.

How to determine the data transfer duration when using Snapmirror / vol copy / aggr copy / ndmpcopy?

Immediate help needed.

[radek_kubka]

Hi and welcome to the Communities!

The (unfortunate) answer is - it varies, as the speed depends on many factors, like the size of the controller, what kind of data (small files, LUNs), etc.

Probably your best bet though is SnapMirror:

- do the baseline transfer without any downtime, for how long it takes

- do subsequent delta updates (as many as you wish)

- when everyone is ready, stop the IO to your source, do the final delta update and switch over to destination

This arguably gives you the shortest possible downtime.

Regards,
Radek

[vreddypalli]

Hi Radek,

Thank you very much for the immediate respone.

The data in question is iSCSI luns and NFS.  For iSCSI we need a downtime to take a consistant snapshot.  One more requirement is to copy all the existing snapshots to the new disk shelfs.

Customer is ready to give downtime but wants to know the approximate duration.

Also the new disk shelf is getting connected to the same controllers we are planning to user "vol copy / aggr copy".  Are there any methods to calculate the tranfer durations for all migration utitlites.

[radek_kubka]

One more requirement is to copy all the existing snapshots to the new disk shelfs.

Again - VSM is your best bet as it transfer across all snaps.

Customer is ready to give downtime but wants to know the approximate duration. 

With VSM it should be really brief (minutes, unless some 'fat fingers' accident happens )

Also the new disk shelf is getting connected to the same controllers we are planning to user "vol copy / aggr copy". 

You can have VSM source and destination behind the same controller (not sure whether that's true for all ONTAP versions, or only newer ones).