[lvm-devel] lvmcache lv destroy with no flush

[Lakshmi Narasimhan Sundararajan]

➢ 1.) remove devices from DM table
➢ dmsetup remove_all
➢ (or just some selected device - whatever fits...)
➢ 
➢ 2.) remove disk singatures of VG
➢ wipefs -a /dev/sdc
➢ wipefs -a /dev/nvme0n1
➢ (or pvremove -ff /dev/sdc /dev/nvme0n1)
➢ 
➢ 3.) recreate empty VG from scratch
➢ vgcreate pxtest /dev/sdc /dev/nvme0n1


myhome$ sudo dmsetup status --target cache
pxtest-pool: 0 20963328 cache 8 40/2048 2048 4096/10220 28 58 0 0 0 0 4096 1 writethrough 2 migration_threshold 2048 cleaner 0 rw -
myhome$ sudo dmsetup remove pxtest-pool
myhome$
myhome$ sudo vgchange -an pxtest
  0 logical volume(s) in volume group "pxtest" now active
myhome$ sudo pvremove -ff /dev/sdc /dev/nvme0n1
Really WIPE LABELS from physical volume "/dev/sdc" of volume group "pxtest" [y/n]? y
  WARNING: Wiping physical volume label from /dev/sdc of volume group "pxtest"
  Can't open /dev/sdc exclusively - not removing. Mounted filesystem?
Really WIPE LABELS from physical volume "/dev/nvme0n1" of volume group "pxtest" [y/n]? y
  WARNING: Wiping physical volume label from /dev/nvme0n1 of volume group "pxtest"
  Can't open /dev/nvme0n1 exclusively - not removing. Mounted filesystem?
myhome$
myhome$ sudo wipefs -a /dev/sdc /dev/nvme0n1
wipefs: error: /dev/sdc: probing initialization failed: Device or resource busy
myhome$


Doesn’t seem to work, there are still exclusive references on the drive held by lvm!
Any other way out?

LN

Sent from Mail for Windows 10

From: Zdenek Kabelac
Sent: Friday, August 2, 2019 7:21 PM
To: Lakshmi Narasimhan Sundararajan; LVM2 development
Subject: Re: [lvm-devel] lvmcache lv destroy with no flush

Dne 02. 08. 19 v 15:45 Lakshmi Narasimhan Sundararajan napsal(a):
> Hi Zdenek,
> 
> Thank you for your email.
> 
>   * If you know you are going to destroy whole VG - you can simply make sure,
>   * there is no running  LV - and just recreate  PV/VG from scratch - certainly
>   * faster them removing i.e.  thousand of LVs individually one-by-one which
>   * is what will happen with lvremove/vgremove command ATM.
> 
> I tried to follow you for accelerated removal… did I interpret you correctly? 
> I though hit the cache sync stuck issue. Please clarify what needs to change 
> below. I see still cache flush happens while removing the vg.
> 
> myhome$ sudo vgcreate pxtest /dev/sdc /dev/nvme0n1
> 
>    Volume group "pxtest" successfully created
> 
> myhome$
> 
> myhome$ sudo lvcreate -n cache --type cache-pool -l 100%pvs pxtest /dev/nvme0n1
> 
>    Logical volume "cache" created.
> 
> myhome$ sudo lvcreate -n pool --type cache --cachepool pxtest/cache -l 100%pvs 
> pxtest /dev/sdc
> 
>    Logical volume "pool" created.
> 
> Myhome$
> 
> myhome$ sudo lvs pxtest
> 
>    LV   VG     Attr       LSize  Pool    Origin       Data%  Meta%  Move Log 
> Cpy%Sync Convert
> 
>    pool pxtest Cwi---C--- 10.00g [cache] [pool_corig]
> 
> myhome$
> 
> myhome$ sudo vgchange -an pxtest
> 
>    0 logical volume(s) in volume group "pxtest" now active
> 
> myhome$ sudo vgremove -ff pxtest
> 
>    4096 blocks must still be flushed.
> 
>    4096 blocks must still be flushed.
> 
>    4096 blocks must still be flushed.
> 
>    4096 blocks must still be flushed.
> 
> ^C
> 

1.) remove devices from DM table
dmsetup remove_all
(or just some selected device - whatever fits...)

2.) remove disk singatures of VG
wipefs -a /dev/sdc
wipefs -a /dev/nvme0n1
(or pvremove -ff /dev/sdc /dev/nvme0n1)

3.) recreate empty VG from scratch
vgcreate pxtest /dev/sdc /dev/nvme0n1


Although I'm not quite sure this is what you really want :) - it's more or 
less idea for quicker testing - not something for presering data.


Regards

Zdenek

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