NAS with RAID 5 on Linux

I currently own a NAS "any" and I want to change to something a little bigger.

Motherboard with a Intel D945GCLF2 mini-ITX (Atom 2x1.6Ghz). Everything runs on Linux with RAID software.

My main issue is that the motherboard has only 2 SATA ports. But I want to have 4 disks of 750 GB SATA RAID 5 and a SSD for the operating system.

What is the best solution? Take a PCI card with 4 SATA ports on which I place the 4 discs and I plug the SSD on a port on the motherboard?

Moreover is it possible to use the hot-plug Linux? Is a SATA controller card for the special hot-plug?

it would not be better to take a true micro atx motherboard with 6 sata? because the material that you have signs it was rather intended to be used as is (not for nothing that the psu is limited), if we begin to add maps and additional hdd, it will soon be blocked (by mini-ITX motherboard and case mini ITX)

in fact, is not really a nas that you want to mount, it is a 24/24 server? with at least one extra virgin hdd (in spare or awaiting swap)?

Indeed, this would be a 24/24 server.

For hard disk, it's 4 disks in Raid 5 for data and a SSD for the system.

The advantage of the mini-ITX is really that congestion is minimized. The case that interests me has 4 slots for hot-plug hard drives. So I guess charge level on the psu it should be playable ...

4 sata accessed simultaneously on the pci port, I think this is frankly not very modern. If we compare to 4 or 6 port sata native, there is no photo, we divide the raw perfs by approximately 4.

for psu, it will be very variable depending on the models of drives (some even have ssd consumption equivalent to a hdd), the worst of the worst with 5 drives and with a greedy pci card it could climb to 90-100w real full charge (without the motherboard, the cpu, the ram, the fans). very low, carefully choosing its drives, you can descend to over 50-60w.

for hotplug, motherboards and hard drives modern agree, I imagine that under linux there is no limitation. in general, there is no need to hot swap box.

that's what I think

Indeed, your first point is interesting. The limitation of PCI is likely to be felt. Nevertheless, the data will be used for a Gigabit network, therefore limiting theoretical 125 Mb/s. Knowing that the PCI bus is 133 MB/s, it is the network that will limit, so is it really a problem?

The discs will be 4 western digital green power. According to tests, it seems to me that they consume about 12W in load, so 48W for 4 discs. If one account with the SSD, we arrive at 55 - 60W. So there is 60W for the motherboard, cpu and ram. I think it should be sufficient (120W).

Thank you for the info on the hot-plug. And do you have an idea of what distribution of linux would be most appropriate?

That you know best?

At this place, I recommend distribution which is not too heavy, stable and efficient: Slackware or Debian.

There are many other alternatives, but really I prefer Slackware.