> I have a 1.5Tb RAID5 machine (3*750Gb disks + 1 spare) and need to > move some write-intensive services there. Unfortunately, the > performance is unacceptable. Thus, I wanted to convert the machine > to RAID10. > > My theory was: backup, remove the spare, set one disk faulty, remove > it, create a degraded RAID10 on the two freed disks, copy data, kill > RAID5, add disks to new RAID10. > > Unfortunately, mdadm (2.5.3) doesn't seem to agree; it complains > that it cannot assemble a RAID10 with 4 devices when I ask it to: > > mdadm --create -l 10 -n4 -pn2 /dev/md1 /dev/sd[cd] missing missing > > I can kind of understand, but on the other hand I don't. After all, > if you'll allow me to think in terms of 1+0 instead of 10 for > a second, why doesn't mdadm just assemble /dev/sd[cd] as RAID0 and > make the couple one of the two components of the RAID1? What I mean > is: I could set up RAID1+0 that way; why doesn't it work for RAID10? > > Do you know of a way in which I could migrate the data to RAID10? > Unfortunately, I do not have more 750Gb disks available nor > a budget, and the 1.5Tb are 96% full. > AFAIK, linux raid-10 is not exactly raid 1+0, it allows you to, for example, use 3 disks. You could create a raid-0, then later add that as a component to a raid-1. A tested backup would certainly be helpful, although it should work without it (and I can easily say that, as it's not my data that will be lost: YMMV!) Jurriaan - 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
