I'm considering using FreeNAS and "recycling" some of my older 1TB disks. Two are the exact same model Western Digital while another is Seagate and the fourth is Samsung.

Typically, since all disks are not equal, I'll create my arrays on a Windows-based server 1GB undersized to prevent a replacement disk not being large enough. Dell is notorious for sending replacement SATA disks of different brand---knock on wood, no problems yet.

Since not all drives are created equally and they can vary a few MBs, is there a way to make the the FreeNas/ZFS/Raid-Z function in the same way I do for my Windows-based servers above?

Thanks