Bug 811348

Summary: raid down conversion gives confusing message when specifying too few images to remove
Product: Red Hat Enterprise Linux 6 Reporter: Corey Marthaler <cmarthal>
Component: lvm2Assignee: Jonathan Earl Brassow <jbrassow>
lvm2 sub component: Mirroring and RAID (RHEL6) QA Contact: Cluster QE <mspqa-list>
Status: CLOSED ERRATA Docs Contact:
Severity: low    
Priority: low CC: agk, dwysocha, heinzm, jbrassow, msnitzer, nperic, prajnoha, prockai, thornber, zkabelac
Version: 6.3   
Target Milestone: rc   
Target Release: ---   
Hardware: x86_64   
OS: Linux   
Whiteboard:
Fixed In Version: lvm2-2.02.107-1.el6 Doc Type: Bug Fix
Doc Text:
No Documentation needed - better error reporting
 Story Points: ---
Clone Of: Environment:
Last Closed: 2014-10-14 08:22:50 UTC Type: Bug
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Bug Depends On:    
Bug Blocks: 1075263    

Description Corey Marthaler 2012-04-10 18:56:54 UTC 
Description of problem:
Basically, when you specify too few mimages to remove during a mirror down convert, LVM picks remaining images to remove in order to complete the requested down convert. However when attempting the same thing in the raid world you just get an error stating now enough rimages to satisfy request. 

This isn't really a big deal other then the behaviors should probably be the same for both types of volumes.


# MIRROR DOWN CONVERT
[root@taft-01 ~]# lvcreate -m 2 -n mirror -L 500M taft
  Logical volume "mirror" created
[root@taft-01 ~]# lvs -a -o +devices
  LV                VG    Attr     LSize   Log         Copy%  Devices
  mirror            taft  mwi-a-m- 500.00m mirror_mlog 100.00 mirror_mimage_0(0),mirror_mimage_1(0),mirror_mimage_2(0)
  [mirror_mimage_0] taft  iwi-aom- 500.00m                    /dev/sdb1(0)
  [mirror_mimage_1] taft  iwi-aom- 500.00m                    /dev/sdc1(0)
  [mirror_mimage_2] taft  iwi-aom- 500.00m                    /dev/sdd1(0)
  [mirror_mlog]     taft  lwi-aom-   4.00m                    /dev/sdh1(0)
[root@taft-01 ~]# lvconvert -m 0 taft/mirror /dev/sdd1
  Logical volume mirror converted.
[root@taft-01 ~]# lvs -a -o +devices
  LV      VG    Attr     LSize   Log Copy%  Devices         
  mirror  taft  -wi-a--- 500.00m            /dev/sdb1(0)    


# RAID DOWN CONVERT
[root@taft-01 ~]# lvcreate -m 2 --type raid1 -n raid -L 500M taft
  Logical volume "raid" created
[root@taft-01 ~]# lvs -a -o +devices
  LV              VG     ttr     LSize   Log Copy%  Devices
  raid            taft   wi-a-m- 500.00m     100.00 raid_rimage_0(0),raid_rimage_1(0),raid_rimage_2(0)
  [raid_rimage_0] taft   wi-aor- 500.00m            /dev/sdb1(1)
  [raid_rimage_1] taft   wi-aor- 500.00m            /dev/sdc1(1)
  [raid_rimage_2] taft   wi-aor- 500.00m            /dev/sdd1(1)
  [raid_rmeta_0]  taft   wi-aor-   4.00m            /dev/sdb1(0)
  [raid_rmeta_1]  taft   wi-aor-   4.00m            /dev/sdc1(0)
  [raid_rmeta_2]  taft   wi-aor-   4.00m            /dev/sdd1(0)
[root@taft-01 ~]# lvconvert -m 0 taft/raid /dev/sdd1
  Unable to extract enough images to satisfy request
  Failed to extract images from taft/raid


Version-Release number of selected component (if applicable):
2.6.32-251.el6.x86_64
lvm2-2.02.95-3.el6    BUILT: Fri Mar 30 09:54:10 CDT 2012
lvm2-libs-2.02.95-3.el6    BUILT: Fri Mar 30 09:54:10 CDT 2012
lvm2-cluster-2.02.95-3.el6    BUILT: Fri Mar 30 09:54:10 CDT 2012
udev-147-2.40.el6    BUILT: Fri Sep 23 07:51:13 CDT 2011
device-mapper-1.02.74-3.el6    BUILT: Fri Mar 30 09:54:10 CDT 2012
device-mapper-libs-1.02.74-3.el6    BUILT: Fri Mar 30 09:54:10 CDT 2012
device-mapper-event-1.02.74-3.el6    BUILT: Fri Mar 30 09:54:10 CDT 2012
device-mapper-event-libs-1.02.74-3.el6    BUILT: Fri Mar 30 09:54:10 CDT 2012
cmirror-2.02.95-3.el6    BUILT: Fri Mar 30 09:54:10 CDT 2012
Comment 1 Jonathan Earl Brassow 2012-04-19 15:41:18 UTC 
Not for 6.3.  For now, users will either have to specify a complete listing or none - no partial listings.  (I actually prefer this method and would rather make mirroring behave like RAID...)
Comment 3 Jonathan Earl Brassow 2012-07-30 22:51:59 UTC 
We'll have to decide which way to go on this issue before fixing this bug.  I prefer the way RAID handles it, but the way mirror does it might be the way we are forced to go due to history.
Comment 7 Alasdair Kergon 2013-10-08 12:51:52 UTC 
Alternatively just leave things how they are.

And I don't find "Unable to extract enough images to satisfy request" particularly helpful.
Comment 9 Jonathan Earl Brassow 2014-03-11 17:14:25 UTC 
I don't mind the difference in behavior, but agk is right that the message should be better.  Perhaps we could count the PV list ahead of time and then tell the user they haven't specified enough PVs.

I'll make this bug about the message then, not the behavior.
Comment 11 Jonathan Earl Brassow 2014-04-03 22:07:20 UTC 
Fix posted upstream:

commit 6c6468f91d9b7a93a85726dfb1b397b555502c1c
Author: Jonathan Brassow <jbrassow>
Date:   Thu Apr 3 16:57:41 2014 -0500

    RAID: Improve an error message
    
    When down-converting a RAID1 LV, if the user specifies too few devices,
    they will get a confusing message.
    Ex:
    [root]# lvcreate -m 2 --type raid1 -n raid -L 500M taft
      Logical volume "raid" created
    
    [root]# lvconvert -m 0 taft/raid /dev/sdd1
      Unable to extract enough images to satisfy request
      Failed to extract images from taft/raid
    
    This patch makes the error message a bit clearer by telling the user
    the count they are trying to remove and the number of devices they
    supplied.
    
    [root@bp-01 lvm2]# lvcreate --type raid1 -m 3 -L 200M -n lv vg
      Logical volume "lv" created
    
    [root@bp-01 lvm2]# lvconvert -m -3 vg/lv /dev/sdb1
      Unable to remove 3 images:  Only 1 device given.
      Failed to extract images from vg/lv
    
    [root@bp-01 lvm2]# lvconvert -m -3 vg/lv /dev/sd[bc]1
      Unable to remove 3 images:  Only 2 devices given.
      Failed to extract images from vg/lv
    
    [root@bp-01 lvm2]# lvconvert -m -3 vg/lv /dev/sd[bcd]1
    [root@bp-01 lvm2]# lvs -a -o name,attr,devices vg
      LV   Attr       Devices
      lv   -wi-a----- /dev/sde1(1)
    
    This patch doesn't work in all cases.  The user can specify the right
    number of devices, but not a sufficient amount of devices from the LV.
    This will produce the old error message:
    [root@bp-01 lvm2]# lvconvert -m -3 vg/lv /dev/sd[bcf]1
      Unable to extract enough images to satisfy request
      Failed to extract images from vg/lv
    However, I think this error message is sufficient for this case.
Comment 13 Nenad Peric 2014-07-08 13:27:55 UTC 
Tested with: 

lvm2-2.02.107-1.el6    BUILT: Mon Jun 23 16:44:45 CEST 2014
lvm2-libs-2.02.107-1.el6    BUILT: Mon Jun 23 16:44:45 CEST 2014
lvm2-cluster-2.02.107-1.el6    BUILT: Mon Jun 23 16:44:45 CEST 2014
udev-147-2.55.el6    BUILT: Wed Jun 18 13:30:21 CEST 2014
device-mapper-1.02.86-1.el6    BUILT: Mon Jun 23 16:44:45 CEST 2014
device-mapper-libs-1.02.86-1.el6    BUILT: Mon Jun 23 16:44:45 CEST 2014
device-mapper-event-1.02.86-1.el6    BUILT: Mon Jun 23 16:44:45 CEST 2014
device-mapper-event-libs-1.02.86-1.el6    BUILT: Mon Jun 23 16:44:45 CEST 2014
device-mapper-persistent-data-0.3.2-1.el6    BUILT: Fri Apr  4 15:43:06 CEST 2014
cmirror-2.02.107-1.el6    BUILT: Mon Jun 23 16:44:45 CEST 2014


The error messages make more sense and behave as described in the last comment (Comment #11).

Marking VERIFIED.
Comment 14 errata-xmlrpc 2014-10-14 08:22:50 UTC 
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

http://rhn.redhat.com/errata/RHBA-2014-1387.html