Hi Maurice, On 06/23/11 18:06, maurice wrote:
What I do NOT know is the following: A) Which is more RELIABLE: R1 with 3 disks or R10 with 3 disks.
R10 has different layouts. There are two components to the layout - where the chunks are located on the different devices (near, offset, far), and number of copies of the data. The near/offset/far part of the layout does not play a role in reliability, just in performance. So, the number of copies is the only thing that matters to this discussion.
If you have R10 with 3 disks and 3 copies, it is equally reliable to R1 with 3 disks, as they have an equal number of copies. In both R10 and R1 in this case, two disks can fail, and you still have 1 intact copy remaining.
B) HOW to create either the 3 disk R1 or R10, assuming an existing 2 disk R1.
If there is an existing R1, and you just want to add an extra device to it, it's easy - you just have to "grow" the array to increase the number of devices, and then "add" a device, and it'll become a 3 device R1. I don't think you'd want to switch to R10 if you are looking to just add a 3rd device to an existing R1!
Example: mdadm --grow -n 3 /dev/md0 mdadm /dev/md0 --add /dev/sdc1 Does that help? Cheers, Iordan -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
