Piergiorgio Sartor wrote: > Hi, > >>> RAID-5/6 with heterogeneous devices. > [...] >> I've thought about this occasionally but don't think much of the idea. >> It seems nice until you think about what happens when devices fail >> and you need to integrate hot spares. >> Clearly any spare will need to be as big as the largest device. >> When that get integrated in place of a small device, you will be >> wasting space on it, and then someone will want to be able to >> grow the array to use that extra space, which would be rather >> messy. >> >> I think it is best to assume that all devices are the same size. >> Trying to support anything else in a useful way would just add >> complexity with little value. > > I see your point and I also agree that complexity > might be too much. > > Nevertheless I disagree about the "wasting space", > since I can see a scenario where there is even > more wasting. > > Let's assume we have a RAID-5 with 7 disks. > Each time an HD fails, we will replace it with a > larger one, since this will be cheaper. > Once we replaced 3 HDs, with could use the unused > space in RAID-5 again. > Unfortunately, with the current features, we will > have to wait to fail all the 7 disks. > So, with 6 HDs replaced with larger ones, we will > have a lot of wasted space. > Of course, unless we did a clever partitioning at > very the beginning. > Or alternatively you use LVM from the start. Then you only need to "cleverly partition" the new drives, use the first partition in the old RAID, use the second partition for a new smaller raid, join the new raid to the VG of the old raid and voilla - no wasted space. -- 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
