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As with paralleled diodes you should balance them - in this case with high value resistors in parallel with each diode - otherwise they won't share equally, and one diode (and then both) WILL fail. Spec wise, current same, voltage double.
Here you can see two non matched diodes and the effects -
1) They have unbalanced power dissipation.
2) In reverse conduction one takes a lot more Vreverse than the other.
3) In forward conduction they have substantially different Vforward drop.
A way or partially equalizing the differences is to start a R in parallel with each
diode. But that leads to higher Ireverse going thru the load which may or may not
be a problem. So you trade off equalization with I reverse, but improve the balance
of Vreverse that the diodes experience.
Note in this example I did not use two of the same diode, so example might be more
extreme, but even using 2 of the same diodes, because of the log Vforward, one might
experience a lot more Pdissipation in one of the diodes, so that would have to be examined.
With 1K's strapped across each diode the Vreverse is much better balanced -
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