[Maakuth]

Z2 means you'll have two parity disks, like in RAID-6. That should be okay. The trouble with RAID-5 are the rebuild times that rise to multiple days with modern disk sizes. The duration of time you run effectively without redundancy grows uncomfortably large. Especially if you don't have a hot or even cold spare around.

[cm2187]

Only if you need high availability, which is probably not the case for home use.

If one of your drives fails under RAID5, before you even order a new disk, you should do an incremental backup, so that your backup is up to date. Then it doesn't really matter that the rebuild times take long. And if you have more data coming in, just do more incremental backups during the rebuild time.

[Mashimo]

Ah yes, I mixed up raid5 and 6.

I think it's still fine for casual home setups. Depending on data and backup strategy.