How long does it typically take to migrate M/S DB to HRD

[rishi]

Since I am evaluating the risk of migration my current prod
application from M/S to HRD, I need to know the following:

1) Using the new hrd migration tool (which says the read-only time
just depends on the write rate), assuming the write rate is almost 0,
how long would it take to complete the migration. If the migration
time is minimal I could do this during my off-peak hrs.

2) Also once the migration is done to a new application could I
continue using the older M/S application while I test the new HRD
application. This is to make sure my prod application on M/S continues
to work while I test our the new HRD datastore.

[Stacy (Google)]

You should do your testing after the initial copy - then go ahead do as much testing as you want before moving on to syncing.

With the new tool, the "sync" operation can be done multiple times - by doing one right after another, you'll get a good indication of what your read-only period will be.

We're still doing the final testing and optimization now, so I can't give any reliable estimates yet, but the blog post will be coming soon.