linux softraid setup which drives are mirrors

#Linux softraid setup which drives are mirrors free#

In fact, if you have hot-swap trays in your machine, you can replace a failed sdb like this:

There is no need to boot from a live CD or similar (you should be able to boot from the degraded array).

#Linux softraid setup which drives are mirrors free#

You are free to continue using the array during the re-sync. Mdraid will then copy the data, and you can watch the status by cat /proc/mdstat. Something like this, assuming sdb1 is the partition on the replacement disk: mdadm -add /dev/md0 /dev/sdb1 To recover your array, you add the new disk/partition to it. In general, all array management is done with mdadm and further it is seldom a good idea to go around mdraid. If you did that, you'd have two disk 1's, or two disk 2's, and mdadm would be confused (and, I haven't tested this, but I assume it'd refuse to assemble the array). This is in fact extremely flexible-you could, for example, remove one of the disks, put it in a USB-SATA enclosure, and attach it to a USB port, and mdraid would still be perfectly happy.Ĭan I recover a degraded array by using dd?

When you (or your distro's boot scripts) do mdadm -assemble on the array, mdadm looks at the metadata on each disk, and from that figures out which is disk 1 and which is disk 2.

You can swap the cables on the two disks. However, the metadata is different it allows mdadm & md to tell the two disks apart. An identical copy of your data is stored on each disk (provided the array is not 'dirty'-e.g., if power is lost after writing to disk 0, but before writing to disk 1).