Greetings!

So I'm moving my Windows file server to Linux. Probably gonna use Ubuntu Server 14. I have a few terabytes worth of data mirrored between two HDDs, just as a form of backup. They're individual drives, no RAID, just kept in sync manually.

I'm pretty certain you can't convert an NTFS volume to ext4 directly, so the best way I could come up with is to delete one of the volumes, mkfs it as ext4, copy the data from the NTFS volume, then delete the NTFS volume, mkfs it as ext4, and copy the data back from the ext4 volume. It's going to take a while, but I don't really care. The only issue I can foresee is if one of the drives dies mid-copy, then I run the risk of losing whatever wasn't copied at the time of the drive's untimely death. It's not "mission-critical" data (music and movies, stuff like that) but I'd hate to lose it nonetheless.

So is my idea the best way of going about it, my main concern being safety?

And speaking of file systems, I have a related question... obviously this is just a home server and only a couple of people use it, so I don't have any exotic needs. I know most Linux distros support a whole bunch of file systems, is ext4 a good choice for my implementation? Or should I consider something like XFS, ZFS, Btrfs, ...? ext4 seems the safe choice since it's the standard file system for most Linux distros, but I'm not really an expert, just a comfortable user.