Re: [gentoo-user] Need a clue about merging logical volumes/groups with lvm2
On Sat, 21 Jul 2012 14:11:03 -0700, walt wrote: I have a 500gig disk that is split roughly in half between two volume groups, each containing four physical volumes, and each vg is formatted into an ext4 filesystem of roughly 250GB. This doesn't make sense, VGs don't have filesystems, they contain LVs and they have the filesystems. What I plan to do is merge the two volume groups into one, containing one big ext4 filesystem, which will contain all of the files currently on the disk. Can this be done without copying one of the existing ext4 filesystems to a separate drive first, and then copying it back after extending the remaining vg/filesystem? (One filesystem has 24GB free and the other has 25GB free.) It can, by moving data from an LV on one VG to an LV on the other, then reducing one LV and VG and increasing the other. But with so little free space, it would take forever, and you'd still end up with a 90%+ full filesytem. If you have a spare drive, I'd add a partition on that to the VG you want to keep, increase the LV size and move everything over. Then remove the VGs from the second disk, add it to the first VG and use pvmove to move everything off the spare disk before removing it from the VG. You can continue to use the system while this runs, so this gives the least downtime with minimal hassle. -- Neil Bothwick Never underestimate the bandwidth of a station wagon full of tapes! signature.asc Description: PGP signature
Re: [gentoo-user] Need a clue about merging logical volumes/groups with lvm2
On Sat, 21 Jul 2012 14:11:03 -0700 walt w41...@gmail.com wrote: I know there are a few lvm2 experts lurking here :) I have a 500gig disk that is split roughly in half between two volume groups, each containing four physical volumes, and each vg is formatted into an ext4 filesystem of roughly 250GB. What I plan to do is merge the two volume groups into one, containing one big ext4 filesystem, which will contain all of the files currently on the disk. Can this be done without copying one of the existing ext4 filesystems to a separate drive first, and then copying it back after extending the remaining vg/filesystem? (One filesystem has 24GB free and the other has 25GB free.) I'm expecting a no but I'd like to be wrong :) For the most part, the answer is no. But to be totally accurate, it can be done - you just have to shuffle partitions and contents around on the disk a lot in this fashion: Move something a bit further towards the end, Extend the thing in front of it to use the now-free space. But be warned, it's a complete PITA and a lot like playing the 15 pieces game with your disk volumes. You have about 10% free space on both vgs, so the odds you can move things around successfully are not good. Get yourself a 500G portable drive to help with the migration. -- Alan McKinnon alan.mckin...@gmail.com
[gentoo-user] Need a clue about merging logical volumes/groups with lvm2
I know there are a few lvm2 experts lurking here :) I have a 500gig disk that is split roughly in half between two volume groups, each containing four physical volumes, and each vg is formatted into an ext4 filesystem of roughly 250GB. What I plan to do is merge the two volume groups into one, containing one big ext4 filesystem, which will contain all of the files currently on the disk. Can this be done without copying one of the existing ext4 filesystems to a separate drive first, and then copying it back after extending the remaining vg/filesystem? (One filesystem has 24GB free and the other has 25GB free.) I'm expecting a no but I'd like to be wrong :)
Re: [gentoo-user] Need a clue about merging logical volumes/groups with lvm2
walt writes: I know there are a few lvm2 experts lurking here :) I have a 500gig disk that is split roughly in half between two volume groups, each containing four physical volumes, and each vg is formatted into an ext4 filesystem of roughly 250GB. What I plan to do is merge the two volume groups into one, containing one big ext4 filesystem, which will contain all of the files currently on the disk. Can this be done without copying one of the existing ext4 filesystems to a separate drive first, and then copying it back after extending the remaining vg/filesystem? (One filesystem has 24GB free and the other has 25GB free.) I'm expecting a no but I'd like to be wrong :) I think you are right. But if you had more free space, it might be possible. So your physical volumes are about 63 G each. If you free that much space on one filesystem, reduce the file system, then reduce the LV, you can use pvmove to move stuff from one PV you want to empty to the others. When done, you can remove the now empty PV from the VG with vgreduce. Then use vgextend to add the PV to the other VG. Extend the LV of that VG and enlarge the file system, copy stuff from the other FS over until you can free another PV. And so on. But copying all stuff of one VG to another location would be much easier. And less error-prone. Wonko
