Gotta hate this first thing Monday morning.
This might be of use check out mdadm man pages.
Tell mdadm that the array pre-existed and is known to be clean. It can be useful when trying to recover from a major failure as you can be sure that no data will be affected unless you actually write to the array. It can also be used when creating a RAID1 or RAID10 if you want to avoid the initial resync, however this practice - while normally safe - is not recommended. Use this ony if you really know what you are doing.
However, I would only mount read only for data recovery, then rebuild the array, if it were me.
Also do you know what caused the 2 drives to fail? It appears (guessing here) that sde2 and sdf2 are a Raid1 set that is part of a larger Raid 0 Volume, is that correct?
When designing Raid 10 (or any Raid for that matter) always look at things like the power and SATA controllers for the drives. For Raid 10 set up each Raid 1 set so that each drive of the set is on a different SATA channel, and different power supply.
In your case, assuming your setup is like this:
sda3, sdb3 - Raid 1 (Set 1)
sdc2, sdd2 - Raid 1 (Set 2)
sde2, sdf2 - Raid 1 (Set 3)
With these three Raid 1 sets part of md0; I would make sure that
sda3, sdc2, sde2 are not connected to the same power or SATA controller as their mirror. This helps to limit the possibility of critical failure like you experienced.
Good luck, please let us know if / how you recover.