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Bug 1518121 - multisegment RAID1, allocator uses one disk for both legs
Summary: multisegment RAID1, allocator uses one disk for both legs
Status: NEW
Alias: None
Product: LVM and device-mapper
Classification: Community
Component: lvm2
Version: 2.02.176
Hardware: Unspecified
OS: Unspecified
Target Milestone: ---
: ---
Assignee: Heinz Mauelshagen
QA Contact:
Depends On:
TreeView+ depends on / blocked
Reported: 2017-11-28 09:11 UTC by Marian Csontos
Modified: 2018-10-18 12:12 UTC (History)
8 users (show)

Fixed In Version:
Doc Type: If docs needed, set a value
Doc Text:
Clone Of:
Last Closed:
rule-engine: lvm-technical-solution?
rule-engine: lvm-test-coverage?

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Description Marian Csontos 2017-11-28 09:11:10 UTC
Description of problem:
When creating RAID1 with 2 legs spanning multiple disks, allocator uses one of the disks for both legs.

Version-Release number of selected component (if applicable):

Affected versions: el7.2, el7.5, not checked other...

How reproducible:

Steps to Reproduce:
- having 3 8GB disks /dev/sd[abc]

    vgcreate vg /dev/sd[abc]
    lvcreate -n t1 -L 4G vg /dev/sda
    lvcreate -n t2 -L 4G vg /dev/sdb
    lvcreate -n r1 -m 1 -L 6G vg
    lvs -aoname,devices

Actual results:

# lvs -aoname,devices
  LV            Devices                      
  r1            r1_rimage_0(0),r1_rimage_1(0)
  [r1_rimage_0] /dev/sdc(1)                  <---- sdc is used for both _rimage_0...
  [r1_rimage_0] /dev/sdb(1024)               
  [r1_rimage_1] /dev/sda(1025)               
  [r1_rimage_1] /dev/sdc(1023)               <---- well as for _rimage_1
  [r1_rmeta_0]  /dev/sdc(0)                  
  [r1_rmeta_1]  /dev/sda(1024)               
  t1            /dev/sda(0)                  
  t2            /dev/sdb(0) 

Expected results:

Additional info:

Comment 1 Marian Csontos 2017-11-28 12:53:58 UTC
In case of failure such device can not be repaired:

# lvconvert --repair vg/r1
  WARNING: Disabling lvmetad cache for repair command.
  WARNING: Not using lvmetad because of repair.
  /dev/vg/r1: read failed after 0 of 4096 at 6442385408: Input/output error
  /dev/vg/r1: read failed after 0 of 4096 at 6442442752: Input/output error
  Couldn't find device with uuid UFK7K0-nGPE-76Rq-F5WC-xGig-UzXP-MnFuDz.
Attempt to replace failed RAID images (requires full device resync)? [y/n]: y
  Unable to replace all PVs from vg/r1 at once.
  Failed to replace faulty devices in vg/r1.

TODO: Test with devices in sync.

Workaround: `lvcreate -n r1 -m 1 -L 6G vg /dev/sd[cab]`

Comment 2 Marian Csontos 2017-11-28 14:23:30 UTC
Waited for sync. 100% in sync unable to repair. Also it is possible to read only first 4 GBs, reading from the second segment fails.

Read from first segment:

# dd if=/dev/vg/r1 of=/dev/null skip=4000 count=1 bs=1M
1+0 records in
1+0 records out
1048576 bytes (1.0 MB) copied, 0.00195199 s, 537 MB/s

Read from second segment fails:

# dd if=/dev/vg/r1 of=/dev/null skip=5000 count=1 bs=1M
dd: error reading ‘/dev/vg/r1’: Input/output error
0+0 records in
0+0 records out
0 bytes (0 B) copied, 0.00201181 s, 0.0 kB/s

Surprisingly the RAID1 device sanity reports DA:

# dmsetup status
vg-r1_rmeta_1: 0 8192 linear 
vg-r1_rimage_1: 0 8372224 linear 
vg-r1_rimage_1: 8372224 4210688 linear 
vg-t2: 0 8388608 linear 
vg-r1_rmeta_0: 0 8192 linear 
vg-r1_rimage_0: 0 8372224 linear 
vg-r1_rimage_0: 8372224 4210688 linear 
vg-t1: 0 8388608 linear 
vg_stacker_OTzj-root: 0 12582912 linear 
vg-r1: 0 12582912 raid raid1 2 DA 12582912/12582912 idle 0 0 -

And for reference only the segments:

# lvs --segments -aolv_name,pe_ranges,le_ranges
  WARNING: Not using lvmetad because a repair command was run.
  /dev/vg/r1: read failed after 0 of 4096 at 6442385408: Input/output error
  /dev/vg/r1: read failed after 0 of 4096 at 6442442752: Input/output error
  Couldn't find device with uuid jDRXQI-jGSW-BAOG-LB3h-aLhd-8fPb-kHbPZf.
  LV            PE Ranges                             LE Ranges                                
  r1            r1_rimage_0:0-1535 r1_rimage_1:0-1535 [r1_rimage_0]:0-1535,[r1_rimage_1]:0-1535
  [r1_rimage_0] [unknown]:1-1022                      [unknown]:1-1022                         
  [r1_rimage_0] /dev/sdb:1024-1537                    /dev/sdb:1024-1537                       
  [r1_rimage_1] /dev/sda:1025-2046                    /dev/sda:1025-2046                       
  [r1_rimage_1] [unknown]:1023-1536                   [unknown]:1023-1536                      
  [r1_rmeta_0]  [unknown]:0-0                         [unknown]:0-0                            
  [r1_rmeta_1]  /dev/sda:1024-1024                    /dev/sda:1024-1024

Comment 3 Steve D 2018-10-18 12:12:26 UTC
I've just been bitten by this for second time, though I swore I specified PVs manually. 2.02.176 (-4.1ubuntu3) on Ubuntu 18.04.

I also hit a whole load of scrub errors last night - the data stored in the fs seems fine, it looks like when I extended the RAID1 LV in question, the extensions didn't get synced. Still investigating that one - may have been triggered by me trying to work around this bug.

Any thoughts / progress?

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