Hello John, I just recognized your name. You helped me out big time understanding Time machine.
This answer is very helpful. I think I see the picture with regard to the software RAID 10, and this answer pins down a lot of it for me, One thing I am curious about. I had been thinking the software RAID 10 provides a decent backup. I thought that is what the mirroring does. Two drives would have to fail for any data loss to occur. I am sure you know all that, so I am really looking for perspective and understanding of why this arrangement is not secure without additional backup.
I am unclear about PCI-connected system drive. I understand the explanation of the need for something other than the 4-drives going into the RAID array, at least for setting it up and keeping as a spare.
What I had in mind is Lycom DT-120 as a carrier for 500GB SAMSUNG SM951. The raid is for storage. My objectives are improve the speed of storage I am running (just a bunch of disks) and to simplify backups. For backups, I have bash scripts running rsync basically running a hacked sort of mirroring. I was thinking the software RAID 10 with four 8TB drives would be an efficient system for what I need. I was planning to keep the OS on the PCIe SSD rig. I also need to add usb 3.0 to this system, I was thinking that would involve a PCI slot, but not necessarily one of the 16-lane ones. I use this system for app development, the video is ok as-is, What I need is a ton of storage that is safe from loss.
What are the options for connecting drives beyond the four bay slots? I know of usb, but I have looked at that only for temporary drives. I guess to attach large external storage there various cases to buy with various kinds of connections. I am thinking on this system that most likely point to putting usb 3 on there and running that out to the external drives.
I have read the PCI setup with the devices I mentioned is a 5-minute breeze, but I do not warnings here lightly.
