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I am currently using a desktop computer as NAS where I have four hdd's which I have in Raid 1 using mdadm. These Raid 1-drives are encrypted using Ubuntu's default encryption (I think it is cryptsetup)
Does Raspberry Pi Model B+ have sufficient CPU and memory to handle both mdadm and encrypted hdds?
Does Raspberry Pi Model B+ have sufficient CPU and memory to handle both mdadm and encrypted hdds?
I'm not an expert on, or even a user of such things, but unless this places significant load on your desktop machine (e.g, runs one core at 25%+ all the time), then sure.
The pi has a single core, 700 Mhz processor. I don't think the I/O can happen fast enough to overwhelm it in this context, which brings up a point worth considering: The pi does not have SATA connectors, nor is is USB 3.0 equipped. So you will be limited to USB 2.0 speeds. Further, the ethernet is on the USB bus. In theory this doesn't matter since the max ethernet speed (100 Mbps) is less than half the maximum bus throughput (480 Mbps1).
I have a USB 3.0 harddrive attached to a B+ which I access via ethernet or wifi using ssh encryption, and the highest speed I can get reliably doing transfers is 3-4 MB/s (i.e., 24-32 Mbps). The drive itself is not encrypted. I don't know if the ssh encryption in the transfer adds any overhead.
1. Wikipedia says this is actually limited to 280 Mbps of data. I've never seen a USB 2.0 device work faster than that.
I expect this can be made to 'work' (you will need 4 x USB-SATA 'dongles'), however throughput will be hopelessly slow ...
All 4 USB ports & Etrhernet (on the B+ or a A/B with external Hub) are linked to a single port on the GPU and all i/o is handled by the CPU byte at a time = unlike PC which has 'stand-alone' interface chips that support DMA direct to RAM (allowing the CPU to 'just do the encoding' and leave the interface hardware to do the data transfers)
The only 'good' thing you have going for you is that your drives are 'nix format = so 'native' Pi drivers - if they were NTFS you would be looking at even more overhard (and even less throughput) ...
Set up an encrypted NAS on Odroid-C2 or Rasbperry 3 with OpenMediaVault
15 pages step by step manual: http://getreu.net/public/downloads/doc/encrypted-raid1-nas/
