> I understand that, if I do it the "standard" way (ie, power down the > system, remove the failing disk, add the replacement disk, then boot > up and use "mdadm --add" to add the new disk to the array) I run the > risk of running into unreadable sectors on one of the other two disks, > and then my RAID5 is kaput. > > What I would really like to do is to be able to add the new HD to the > array WITHOUT removing the failing HD, somehow sync it with the rest, > and THEN remove the failing HD: that way, an eventual failed read from > one of the two other HDs could possibly be satisfied from the failing > HD (unless EXACTLY that same sector is also unreadable on it, which I > find unlikely), and so avoid losing the whole array in the above case. A reshape from RAID5 -> RAID6 -> RAID5 will hammer your disks so if either of the other two are ready to die, this will most likely tip them over the edge. A far simpler way would be to take the array offline, dd (or dd_rescue) the old drive's contents onto the new disk, pull the old disk, and restart the array with the new drive in it's place. With luck you won't need a resync *and* you're not hammering the other two drives in the process. -- Drew "Nothing in life is to be feared. It is only to be understood." --Marie Curie "This started out as a hobby and spun horribly out of control." -Unknown -- 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
