[linux-lvm] lvm2 raid volumes

Mon Aug 15 13:38:06 UTC 2016

Heinz Mauelshagen schreef op 03-08-2016 15:10:

> The Cyp%Sync field tells you about the resynchronization progress,
> i.e. the initial mirroring of
> all data blocks in a raid1/10 or the initial calculation and storing
> of parity blocks in raid4/5/6.

Heinz, can I perhaps ask you here. If I can.

I have put a root volume on raid 1. Maybe "of course" the second disk 
(LVM volumes) are not available at system boot:

aug 15 14:09:19 xenpc2 kernel: device-mapper: raid: Loading target 
version 1.7.0
aug 15 14:09:19 xenpc2 kernel: device-mapper: raid: Failed to read 
superblock of device at position 1
aug 15 14:09:19 xenpc2 kernel: md/raid1:mdX: active with 1 out of 2 
mirrors
aug 15 14:09:19 xenpc2 kernel: created bitmap (15 pages) for device mdX
aug 15 14:09:19 xenpc2 kernel: mdX: bitmap initialized from disk: read 1 
pages, set 19642 of 30040 bits
aug 15 14:09:19 xenpc2 kernel: EXT4-fs (dm-6): mounted filesystem with 
ordered data mode. Opts: (null)

This could be because I am using PV directly on disk (no partition 
table) for *some* volumes (actually the first disk, that is booted 
from), however, I force a start of LVM2 service by enabling it in 
SystemD:

aug 15 14:09:19 xenpc2 systemd[1]: Starting LVM2...

This is further down the log, so LVM is actually started after the RAID 
is loading.

At that point normally, from my experience, only the root LV is 
available.

Then at a certain point more devices become available:

aug 15 14:09:22 xenpc2 systemd[1]: Found device /dev/mapper/msata-boot.
aug 15 14:09:22 xenpc2 systemd[1]: Started LVM2.

aug 15 14:09:22 xenpc2 systemd[1]: Found device /dev/raid/tmp.
aug 15 14:09:22 xenpc2 systemd[1]: Found device /dev/raid/swap.
aug 15 14:09:22 xenpc2 systemd[1]: Found device /dev/raid/var.

But just before that happens, there are some more RAID1 errors:

aug 15 14:09:22 xenpc2 kernel: device-mapper: raid: Failed to read 
superblock of device at position 1
aug 15 14:09:22 xenpc2 kernel: md/raid1:mdX: active with 1 out of 2 
mirrors
aug 15 14:09:22 xenpc2 kernel: created bitmap (1 pages) for device mdX
aug 15 14:09:22 xenpc2 kernel: mdX: bitmap initialized from disk: read 1 
pages, set 320 of 480 bits
aug 15 14:09:22 xenpc2 kernel: device-mapper: raid: Failed to read 
superblock of device at position 1
aug 15 14:09:22 xenpc2 kernel: md/raid1:mdX: active with 1 out of 2 
mirrors
aug 15 14:09:22 xenpc2 kernel: created bitmap (15 pages) for device mdX
aug 15 14:09:22 xenpc2 kernel: mdX: bitmap initialized from disk: read 1 
pages, set 19642 of 30040 bits

Well small wonder if the device isn't there yet. There are no messages 
for it, but I will assume the mirror LVs came online at the same time as 
the other "raid" volume group LVs, which means the RAID errors preceded 
that.

Hence, no secondary mirror volumes available, cannot start the raid, 
right.

However after logging in, the Cpy%Sync behaviour seems normal:

   boot     msata  rwi-aor--- 240,00m                                    
100,00
   root     msata  rwi-aor---  14,67g                                    
100,00

Devices are shown as:

   boot msata rwi-aor--- 240,00m                                    
100,00           boot_rimage_0(0),boot_rimage_1(0)
   root msata rwi-aor---  14,67g                                    
100,00           root_rimage_0(0),root_rimage_1(0)

dmsetup table seems normal:

# dmsetup table | grep msata | sort
coll-msata--lv: 0 60620800 linear 8:36 2048
msata-boot: 0 491520 raid raid1 3 0 region_size 1024 2 252:14 252:15 - -
msata-boot_rimage_0: 0 491520 linear 8:16 4096
msata-boot_rimage_1: 0 491520 linear 252:12 10240
msata-boot_rimage_1-missing_0_0: 0 491520 error
msata-boot_rmeta_0: 0 8192 linear 8:16 495616
msata-boot_rmeta_1: 0 8192 linear 252:12 2048
msata-boot_rmeta_1-missing_0_0: 0 8192 error
msata-root: 0 30760960 raid raid1 3 0 region_size 1024 2 252:0 252:1 - -
msata-root_rimage_0: 0 30760960 linear 8:16 512000
msata-root_rimage_1: 0 30760960 linear 252:12 509952
msata-root_rimage_1-missing_0_0: 0 30760960 error
msata-root_rmeta_0: 0 8192 linear 8:16 503808
msata-root_rmeta_1: 0 8192 linear 252:12 501760
msata-root_rmeta_1-missing_0_0: 0 8192 error

But actually it's not because it should reference 4 devices, not two. 
Apologies.

It only references the volumes of the first disk (image and meta).

E.g. 252:0 and 252:1 are:

lrwxrwxrwx 1 root root       7 aug 15 14:09 msata-root_rmeta_0 -> 
../dm-0
lrwxrwxrwx 1 root root       7 aug 15 14:09 msata-root_rimage_0 -> 
../dm-1

Whereas the volumes from the other disk are:

lrwxrwxrwx 1 root root       7 aug 15 14:09 msata-root_rmeta_1 -> 
../dm-3
lrwxrwxrwx 1 root root       7 aug 15 14:09 msata-root_rimage_1 -> 
../dm-5

If I dismount /boot, lvchange -an msata/boot, lvchange -ay msata/boot, 
it loads correctly:

aug 15 14:56:23 xenpc2 kernel: md/raid1:mdX: active with 1 out of 2 
mirrors
aug 15 14:56:23 xenpc2 kernel: created bitmap (1 pages) for device mdX
aug 15 14:56:23 xenpc2 kernel: mdX: bitmap initialized from disk: read 1 
pages, set 320 of 480 bits
aug 15 14:56:23 xenpc2 kernel: RAID1 conf printout:
aug 15 14:56:23 xenpc2 kernel:  --- wd:1 rd:2
aug 15 14:56:23 xenpc2 kernel:  disk 0, wo:0, o:1, dev:dm-15
aug 15 14:56:23 xenpc2 kernel:  disk 1, wo:1, o:1, dev:dm-19
aug 15 14:56:23 xenpc2 kernel: RAID1 conf printout:
aug 15 14:56:23 xenpc2 kernel:  --- wd:1 rd:2
aug 15 14:56:23 xenpc2 kernel:  disk 0, wo:0, o:1, dev:dm-15
aug 15 14:56:23 xenpc2 kernel:  disk 1, wo:1, o:1, dev:dm-19
aug 15 14:56:23 xenpc2 kernel: md: recovery of RAID array mdX
aug 15 14:56:23 xenpc2 kernel: md: minimum _guaranteed_  speed: 1000 
KB/sec/disk.
aug 15 14:56:23 xenpc2 kernel: md: using maximum available idle IO 
bandwidth (but not more than 200000 KB/sec) for recovery.
aug 15 14:56:23 xenpc2 kernel: md: using 128k window, over a total of 
245760k.
aug 15 14:56:23 xenpc2 systemd[1]: Starting File System Check on 
/dev/mapper/msata-boot...
aug 15 14:56:23 xenpc2 systemd[1]: Started File System Check Daemon to 
report status.
aug 15 14:56:23 xenpc2 systemd-fsck[6938]: /dev/mapper/msata-boot: 
clean, 310/61440 files, 121269/245760 blocks
aug 15 14:56:23 xenpc2 systemd[1]: Started File System Check on 
/dev/mapper/msata-boot.
aug 15 14:56:23 xenpc2 systemd[1]: Mounting /boot...
aug 15 14:56:23 xenpc2 kernel: EXT4-fs (dm-20): mounting ext2 file 
system using the ext4 subsystem
aug 15 14:56:23 xenpc2 kernel: EXT4-fs (dm-20): mounted filesystem 
without journal. Opts: (null)
aug 15 14:56:23 xenpc2 systemd[1]: Mounted /boot.
aug 15 14:56:26 xenpc2 kernel: md: mdX: recovery done.
aug 15 14:56:26 xenpc2 kernel: RAID1 conf printout:
aug 15 14:56:26 xenpc2 kernel:  --- wd:2 rd:2
aug 15 14:56:26 xenpc2 kernel:  disk 0, wo:0, o:1, dev:dm-15
aug 15 14:56:26 xenpc2 kernel:  disk 1, wo:0, o:1, dev:dm-19

Maybe this whole thing is just caused by the first disk being 
partitionless.

msata-boot: 0 491520 raid raid1 3 0 region_size 1024 2 252:14 252:15 
252:17 252:19

I don't know how LVM is activated under SystemD. This is currently the 
initial startup:

   dev-mapper-msata\x2droot.device (2.474s)
   init.scope
   -.mount
   -.slice
   swap.target
   dm-event.socket
   system.slice
   lvm2-lvmpolld.socket
   systemd-udevd-kernel.socket
   systemd-initctl.socket
   systemd-journald-audit.socket
   lvm2-lvmetad.socket
   systemd-journald.socket
   systemd-modules-load.service (199ms)
   dev-mqueue.mount (66ms)
   ufw.service (69ms)
   systemd-fsckd.socket
   proc-sys-fs-binfmt_misc.automount
   lvm2.service (3.237s)

I have had to enable the SysV lvm2 service and replace vgchange -aay 
--sysinit with just vgchange -aay or it wouldn't work.

lvmetad is started later, but without the manual lvm2 activation, my 
devices just wouldn't get loaded (on multiple systems, ie. when using a 
PV directly on disk to boot from).

No one else boots directly from PV, so I may be the only one to ever 
have experienced this.

But at this point, my mirrors don't work. They do work when not started 
as the main system. So If I boot from another disk, they work.

At least I think they do.

Basically all my LVM volumes are not loaded fast enough before the RAID 
is getting started.

LVM itself gives no indication of error. lvchange --syncaction check 
msata/root does not produce any data. It seems it doesn't notice that 
the RAID hasn't been started.

Again, there is zero output from commands such as lvs -a -o+lv_all and 
yet this is the output from dmsetup table:

msata-root: 0 30760960 raid raid1 3 0 region_size 1024 2 252:0 252:1 - -

So my first question is really: can I restore the RAID array while the 
system is running? E.g. while root is mounted?

I haven't explored the initramfs yet to see why my LVM volumes are not 
getting loaded.

Regards.