On Mon, Apr 10 2017, Wakko Warner wrote: > I have a question about shrinking an array. My current array is 4x 2tb > disks in raid6 (md0). The array was created on the 2nd partition of each > disk and spans most of the disk. I would like to replace the 2tb disks with > 750gb disks. md0 is a luks container with lvm underneath. I have less than > 1tb actually in use. What would the recommended procedure be for shrinking > this? I've watched this list, but I don't think I've come across anyone > actually wanting to do this before. > I'm thinking of these steps already: > 1) Shrink PV. > 2) Shrink luks. I'm aware that there is not size metadata, but the dm > mapping would need to be shrunk. > 3) Shrink md0. I did this once when I changed a 6 drive raid6 into a 5 > drive raid6. Would I use --array-size= or --size= ? I understand the > difference is the size of md0 vs the individual members. You don't need --array-size, as reducing --size is non-destructive. Reducing the number of devices *is* destructive, so if you were to do that, you would need to adjust the --array-size first. So when you have prepared the contents of the array, use mdadm /dev/mdXXX --grow --size=750G or whatever size you think is appropriate. Then check that all your data is still accessible. e.g. fsck your filesystem. If you are confident that the data is still accessible, you can continue to --replace devices. If not, you can mdadm /dev/mdXXX --grow --size=max to restore the previous state, and then try to figure out what went wrong. NeilBrown > > So for number 4, if md0 is now small enough, will it accept a member that is > smaller? If so, I should beable to add the member to the array and issue > --replace. > > Thanks. > > -- > Microsoft has beaten Volkswagen's world record. Volkswagen only created 22 > million bugs. > -- > 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
Attachment:
signature.asc
Description: PGP signature
