Adam Goryachev wrote: > On 11/04/17 10:30, 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. > > > >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. > > > I think the order is wrong.... or I mis-understood the layering. You > need to shrink the highest layer first and work down the stack, for > LVM on luks on RAID it would be something like this: > 1) Reduce the filesystem size > 2) Reduce the LV size > 3) Reduce the PV size > 4) Reduce the luks size > 5) Reduce the RAID (mdadm) size > 6) Replace the physical devices with smaller ones (or reduce the > partition size/etc as needed) Thanks, however, 1 and 2 doesn't need to happen. I deleted several LVs. My highest PE in use is 771583 (each extent is 1M) and the last lv could be moved somewhere else which would leave my highest PE 87982. > I generally reduce my each one with a decent margin, and then when > I'm finished, I increase each one to fill the available space (after > the physical device size is changed). This avoids issues with > accidentally trimming too much and then losing data/corrupting data. > You should also verify that all your data is accessible after each > step, most steps are reversible if you identify the issue quickly > enough (at least with simple stacks when changing partition size, > LVM and/or luks might complicate that). I'm not that concerned about the LV that is at the highest PE range. If I loose it, I loose it. it's the reduce the raid size I was wondering about. Can you give me an example of the command to run for it? I would be interested in doing this while the system is running (it only has 1180 days uptime =) However, I don't have the replacement disks yet. I wanted ideas before I actually do it. -- 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
