Feature request: LVM mirror/RAID volumes

[robbat2]

Please add a check for mirrored/RAID'd LVM volumes.

[glensc]

please see #134. is that what you had in mind?

[glensc]

i think the lvm plugin there is misnamed. the doc for the subsystem seems to be this:
https://www.kernel.org/doc/Documentation/device-mapper/dm-raid.txt

so rename lvm -> dmraid plugin would be more appropriate?, but there already exists dmraid plugin...

[glensc]

ok, perhaps dm (as for device-mapper) as plugin name here?

[robbat2]

DM is a good name for it yes; it does need to cover a lot more device-mapper types.
The 'mirror' type is not the same as the 'raid; type

[glensc]

how would you call the check for documentation purposes? Linux LVM RAID (3f8664e) seems incorrect and confusing? also do you have more doc links on this topic? and perhaps what's the difference with /dev/md* based raid?

[robbat2]

I'd say rather than passing dmsetup status --target=$X, the check should be reading ALL of dmsetup status; then call the check simply device-mapper.

Linux LVM Mirrors
https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/6/html/Logical_Volume_Manager_Administration/mirror_create.html

Linux LVM RAID
https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/6/html/Logical_Volume_Manager_Administration/raid_volumes.html

Low-level:
https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/6/html/Logical_Volume_Manager_Administration/device_mapper.html#mirror-map
https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/6/html/Logical_Volume_Manager_Administration/device_mapper.html#dmraid-map

[glensc]

#134 (comment)
so parsing this and looking docs, seems there's optional #logargs, which are empty in all samples, going go be hard to handle this without whitelisting all known parameters?

i.e the mirror target has: start length mirror log_type #logargs logarg1 ... logargN #devs device1 offset1 ... deviceN offsetN, your sample has just device, not even offset... confusing!

[glensc]

i wonder is there easier way to obtain this info? udev? as otherwise will end up writing drivers/md logic from all modules here, i.e iterate over status of each target: dm-raid1, dm-raid

in pld-linux have some patch (originating from SuSE) for dmsetup export, but that seems to support only specific devices.

[glensc]

ok, so wrote dm-raid1 and dm-raid based parser (committed to master), please have look! fragile, but might just work for some time

[robbat2]

Don't confuse the output of dmsetup table with that of dmsetup status. They are different :-(.

Here's a better test setup, that shows the variations in a nicer way.

# LVC="lvcreate -L 1g --alloc anywhere"
# $LVC --type raid1 -n raid1 vg
# $LVC --type raid5 -n raid5 vg
# $LVC --type raid6 -n raid6 -i 3 vg
# $LVC --type mirror -n mirror-mirrorlog-core --mirrorlog core vg
# $LVC --type mirror -n mirror-mirrorlog-disk --mirrorlog disk vg
# $LVC --type mirror -n mirror-mirrorlog-mirrored --mirrorlog mirrored vg
# dmsetup table |grep -e raid -e mirror |sort
vg-mirror--mirrorlog--core: 0 2097152 mirror core 1 1024 2 254:57 0 254:58 0 1 handle_errors
vg-mirror--mirrorlog--core_mimage_0: 0 2097152 linear 9:4 453707776
vg-mirror--mirrorlog--core_mimage_1: 0 2097152 linear 8:4 12773853184
vg-mirror--mirrorlog--disk: 0 2097152 mirror disk 2 254:60 1024 2 254:61 0 254:62 0 1 handle_errors
vg-mirror--mirrorlog--disk_mimage_0: 0 2097152 linear 9:4 455804928
vg-mirror--mirrorlog--disk_mimage_1: 0 2097152 linear 8:4 12775950336
vg-mirror--mirrorlog--disk_mlog: 0 8192 linear 9:10 1058816
vg-mirror--mirrorlog--mirrored: 0 2097152 mirror disk 2 254:66 1024 2 254:67 0 254:68 0 1 handle_errors
vg-mirror--mirrorlog--mirrored_mimage_0: 0 2097152 linear 9:4 457902080
vg-mirror--mirrorlog--mirrored_mimage_1: 0 2097152 linear 8:4 12778047488
vg-mirror--mirrorlog--mirrored_mlog: 0 8192 mirror core 1 1024 2 254:64 0 254:65 0 1 handle_errors
vg-mirror--mirrorlog--mirrored_mlog_mimage_0: 0 8192 linear 9:4 167659520
vg-mirror--mirrorlog--mirrored_mlog_mimage_1: 0 8192 linear 8:4 12780144640
vg-raid1: 0 2097152 raid raid1 3 0 region_size 1024 2 254:34 254:35 254:36 254:37
vg-raid1_rimage_0: 0 2097152 linear 9:4 450897920
vg-raid1_rimage_1: 0 2097152 linear 8:4 12770699264
vg-raid1_rmeta_0: 0 8192 linear 9:4 450889728
vg-raid1_rmeta_1: 0 8192 linear 8:4 12770691072
vg-raid5: 0 2097152 raid raid5_ls 3 128 region_size 1024 3 254:39 254:40 254:41 254:42 254:43 254:44
vg-raid5_rimage_0: 0 1048576 linear 9:4 165898240
vg-raid5_rimage_1: 0 1048576 linear 8:4 12772804608
vg-raid5_rimage_2: 0 1048576 linear 9:10 10240
vg-raid5_rmeta_0: 0 8192 linear 9:4 165890048
vg-raid5_rmeta_1: 0 8192 linear 8:4 12772796416
vg-raid5_rmeta_2: 0 8192 linear 9:10 2048
vg-raid6: 0 2113536 raid raid6_zr 3 128 region_size 1024 5 254:46 254:47 254:48 254:49 254:50 254:51 254:52 254:53 254:54 254:55
vg-raid6_rimage_0: 0 704512 linear 9:4 761538560
vg-raid6_rimage_1: 0 704512 linear 9:4 304097280
vg-raid6_rimage_2: 0 704512 linear 9:4 453003264
vg-raid6_rimage_3: 0 704512 linear 9:4 166955008
vg-raid6_rimage_4: 0 704512 linear 8:4 14096058368
vg-raid6_rmeta_0: 0 8192 linear 9:4 761530368
vg-raid6_rmeta_1: 0 8192 linear 9:4 304089088
vg-raid6_rmeta_2: 0 8192 linear 9:4 452995072
vg-raid6_rmeta_3: 0 8192 linear 9:4 166946816
vg-raid6_rmeta_4: 0 8192 linear 8:4 14096050176
# dmsetup status |grep -e raid -e mirror |sort
vg-mirror--mirrorlog--core: 0 2097152 mirror 2 254:57 254:58 2048/2048 1 AA 1 core
vg-mirror--mirrorlog--core_mimage_0: 0 2097152 linear 
vg-mirror--mirrorlog--core_mimage_1: 0 2097152 linear 
vg-mirror--mirrorlog--disk: 0 2097152 mirror 2 254:61 254:62 730/2048 1 AA 3 disk 254:60 A
vg-mirror--mirrorlog--disk_mimage_0: 0 2097152 linear 
vg-mirror--mirrorlog--disk_mimage_1: 0 2097152 linear 
vg-mirror--mirrorlog--disk_mlog: 0 8192 linear 
vg-mirror--mirrorlog--mirrored: 0 2097152 mirror 2 254:67 254:68 1328/2048 1 AA 3 disk 254:66 A
vg-mirror--mirrorlog--mirrored_mimage_0: 0 2097152 linear 
vg-mirror--mirrorlog--mirrored_mimage_1: 0 2097152 linear 
vg-mirror--mirrorlog--mirrored_mlog: 0 8192 mirror 2 254:64 254:65 8/8 1 AA 1 core
vg-mirror--mirrorlog--mirrored_mlog_mimage_0: 0 8192 linear 
vg-mirror--mirrorlog--mirrored_mlog_mimage_1: 0 8192 linear 
vg-raid1: 0 2097152 raid raid1 2 AA 2097152/2097152 idle 0
vg-raid1_rimage_0: 0 2097152 linear 
vg-raid1_rimage_1: 0 2097152 linear 
vg-raid1_rmeta_0: 0 8192 linear 
vg-raid1_rmeta_1: 0 8192 linear 
vg-raid5: 0 2097152 raid raid5_ls 3 AAA 1048576/1048576 idle 0
vg-raid5_rimage_0: 0 1048576 linear 
vg-raid5_rimage_1: 0 1048576 linear 
vg-raid5_rimage_2: 0 1048576 linear 
vg-raid5_rmeta_0: 0 8192 linear 
vg-raid5_rmeta_1: 0 8192 linear 
vg-raid5_rmeta_2: 0 8192 linear 
vg-raid6: 0 2113536 raid raid6_zr 5 AAAAA 704512/704512 idle 0
vg-raid6_rimage_0: 0 704512 linear 
vg-raid6_rimage_1: 0 704512 linear 
vg-raid6_rimage_2: 0 704512 linear 
vg-raid6_rimage_3: 0 704512 linear 
vg-raid6_rimage_4: 0 704512 linear 
vg-raid6_rmeta_0: 0 8192 linear 
vg-raid6_rmeta_1: 0 8192 linear 
vg-raid6_rmeta_2: 0 8192 linear 
vg-raid6_rmeta_3: 0 8192 linear 
vg-raid6_rmeta_4: 0 8192 linear 

[glensc]

indeed, the docs i read were about dmsetup table, but i implemented parser based on dmsetup status by reverse-engineering kernel sourcecode. it should be correct. i also committed in parser from your test data.