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May
20
accepted Command 'pvs' says PV device not found, but LVs are mapped and mounted
May
19
comment Why does btrfs refuse to convert metadata to RAID1
I only recently started looking at BTRFS. Having converted an ext4 filesystem, I wanted to upgrade the metadata to DUP, and spent some time trying to figure out what I was doing wrong and why it stubbornly stayed as SINGLE! Now I know.
May
19
answered Command 'pvs' says PV device not found, but LVs are mapped and mounted
May
19
revised Command 'pvs' says PV device not found, but LVs are mapped and mounted
Added pvscan with lvmetad stopped
May
19
revised Command 'pvs' says PV device not found, but LVs are mapped and mounted
Update with additional info
May
18
comment Command 'pvs' says PV device not found, but LVs are mapped and mounted
@Bratchley: my point is that you were suggesting something I'd already tried. If you have a suggestion as to how I can get more detailed information, without simply rebooting, then I'd be happy to try it. Currently pvscan -vvvv (with or without lvm2-lvmetad running) doesn't reference the 'missing' RAID device except to add it to the device cache and note its aliases. pvdisplay -vvvv /dev/md99 obviously finds the device, as it reports the correct UUID, VG, etc from libdm-config.c near the start, but then reports "Failed to find physical volume" at the end!
May
18
comment Command 'pvs' says PV device not found, but LVs are mapped and mounted
@Bratchley, by the way, if you read my comment to derobert, you'd have realised that I've already tried a pvscan (several times).
May
18
comment Command 'pvs' says PV device not found, but LVs are mapped and mounted
I've been using LVM for about 5 years; I know what pvscan is. My point was that I wanted to avoid rebooting the machine since that will almost certainly fix the problem. What I wanted was some way to get LVM back to a consistent state without rebooting. I get the impression this isn't possible. Since LVs in the 'missing' VG can be mounted, I've taken the precaution of copying the data to a new set of LVs in a new VG and will probably reboot later this evening. I expect this will fix the issue, but won't provide info as to why it happened in the first place and if an online fix can be done.
May
18
comment Command 'pvs' says PV device not found, but LVs are mapped and mounted
That would involve a reboot, which would probably fix it. I was hoping to just fix the current state, e.g.by restarting lvmetad (which didn't fix it).
May
17
comment Command 'pvs' says PV device not found, but LVs are mapped and mounted
No filters and obtain_device_list_from_udev is 1. Stopping lvmetad and then doing a pvscan finda duplicate UUD of one of the component devices of the RAID device which make up the RAID10 aary, but the checksum is wrong. It then goes back to saying 'No device found...'.
May
17
asked Command 'pvs' says PV device not found, but LVs are mapped and mounted
Apr
15
comment Can BTRFS stripe RAID arrays?
A quick review of the btrfs wiki (btrfs.wiki.kernel.org/index.php/…) indicates that, once it is stable, btrfs will be able to reshape raid arrays, i.e. add and remove elements from a raid array without loss of data. This is a piece missing from ZFS so clearly makes it the better choice.
Apr
15
comment Can BTRFS stripe RAID arrays?
Thanks for the information. After playing with the btrfs space allocator its clear that the information I was missing was that btrfs automatically stripes the data. AFAIK, md can only use equal size elements (in fact the current version warns if any element differs in size by more than 1%). If I understand correctly, btrfs automatically does the equivalent of mdadm /dev/md0 -C lraid5 -n4 /dev/sd{a,b,c,d}1;mdadm /dev/md1 -C -lraid5 -n3 /dev/sd{a,b,c}2;mdadm /dev/md2 -C -lmirror /dev/sd{a,b}3 plus create the volume. I obviously need to read up on it a bit more! (as well as waiting a while...)
Apr
11
awarded  Nice Answer
Apr
8
comment Does ZFS for Linux over stress VirtualBox?
Thanks for the comment. That's the information I was looking for. I suspect that most people who've run ZFS (or ZoL) in a VM have just tried a few simple operations and haven't tried moving hundreds of files into pools running on raid sets. The only reference I found said it was a timing issue in VirtualBox which it was thought had been fixed, but was then reopened. I suspect ZFS is just pushing the simulation to its limit, expecting it to behave like real hardware. Now I've got most files in place in the VM, the errors have (mostly) stopped.
Apr
7
revised Does ZFS for Linux over stress VirtualBox?
added 1 character in body
Apr
7
awarded  Curious
Apr
6
revised Does ZFS for Linux over stress VirtualBox?
Added ZFS version
Apr
6
asked Does ZFS for Linux over stress VirtualBox?
Mar
25
awarded  Nice Answer