Which is faster - migrating or building from scratch?

[mikesmith_inFL]

Hi,
I've got an old TS-431+ (QTS 4.3.6) that had/has 2 3TB drives in RAID1 and they're labeled DataVol1.
There's about 2.6TB of files (mostly video, some photos, music & misc)

Before I started, I did a complete backup copy to an external drive. That took about 5 or 6 hours.

I'm switching to 4 4TB WD EFRX drives and have started a migration from RAID1 to 5 by adding 2 of the new 4TB drives.
So far it looks like the estimate is about 40 hours to add them. I'm only guesssing but expect it to take the same time
when I replace the old drives with the new ones. ( Is that right? )

Does anyone know if it would take as long to just build the new RAID5 with the 4 new drives and then copy the files back?
I spent most of yesterday and this AM trying to find info about how long operations take, but had no luck finding anything.

I've got no idea about how long a raw build in this configuration would take.

Thanks

[dolbyman]

migration/expansion will take longer than wipe/restore, but the NAS is available the whole time, not so when you start it from scratch.

[mikesmith_inFL]

Thanks!
I didn't even think to check on that. I try to avoid assuming things, I know what it implies.
That makes my decision quite simple.
I'll just continue with the migration.