What are the pros/cons of software raid made up disk connected over SATA and others over USB?

Question

I would like to use RAID1 with 1 SATA disk and 2 USB disks

PS: This is an ARM board (cubietruck) with only 1 SATA port and 2 USB ports.

PS2: The OS boots from a SD card :)

PS3: The setup does not aim for speed but for data reliability.

Edit: I removed the 3rd spare disk (over usb)

Should this question go to superuser.com ? – David Andreoletti Dec 22 '13 at 16:17 — David Andreoletti, Dec 22 '13 at 16:17

score 2 · Accepted Answer · answered Dec 22 '13 at 09:41

2

I can't think of any pros.

The cons are:

you're trying to make a RAID with disks on buses of two vastly different speeds
you're trying to make a RAID with a bus that has notoriously poor low-level drive discipline options (USB)
given the bandwidth limits of the USB bus, you would risk swamping the controller (particularly given that you want your spare on there) and corrupting the array regularly
you're introducing a "spare disk" to a RAID 1 setup, which doesn't really make much sense (they're both already "spare" in a RAID 1)

Basically, you're taking one fast disk and two slow disks, slowing them all down to the speed of the slow disk, and limiting yourself to the size of the smallest disk, while introducing new points of failure, and getting no benefit from it that I can see. Just use the USB disks as backups.

answered Dec 22 '13 at 09:41

Bandrami

893
4
9

Would it be better if the SATA port was not used to avoid swamping ? PS: I meant an additional disk to mirror to instead of spare. – David Andreoletti Dec 22 '13 at 09:55
All of Bandrami's points are good. Either make backups, or check if tour SATA controller supports using [Port multiplication](http://en.wikipedia.org/wiki/Port_multiplier) and use two SATA disks. – Hennes Dec 22 '13 at 12:10
@Bandrami: I will check for port multiplication. – David Andreoletti Dec 22 '13 at 16:19
USB isn't necessarily "vastly" slower (if it's USB 3). – Dave Burton Nov 09 '14 at 21:18

What are the pros/cons of software raid made up disk connected over SATA and others over USB?

1 Answers1