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Today's Topics:

   1. sata cable disconnect + hotplug after (Xen)
   2. Re: lvm2 raid volumes (Xen)
   3. Re: Snapshots & data security (Zdenek Kabelac)
   4. lvm2 cluster aware (su liu)
   5. Re: lvm2 cluster aware (Digimer)


----------------------------------------------------------------------

Message: 1
Date: Tue, 09 Aug 2016 11:58:35 +0200
From: Xen <list@xenhideout.nl>
To: Linux lvm <linux-lvm@redhat.com>
Subject: [linux-lvm] sata cable disconnect + hotplug after
Message-ID: <16a575c3fb60f2579ab1687540cea01e@dds.nl>
Content-Type: text/plain; charset=US-ASCII; format=flowed

What am I supposed to do when a sata cable disconnects and reconnects as
another device?

I had a disk at probably /dev/sda.

At a certain point the filesystem had become read-only. I realized the
cable must have disconnected and after fixing it the same device was now
at /dev/sdf.

Now the device had gone missing from the system but it would not refind
it.

# pvscan
   WARNING: Device for PV fEGbBn-tbIp-rL7y-m22b-1rQh-r9i5-Qwlqz7 not
found or rejected by a filter.
   PV unknown device                VG xenpc1          lvm2 [600,00 GiB /
158,51 GiB free]

pvck clearly found it and lvmdiskscan also found it. Nothing happened
until I did pvscan --cache /dev/sdf:

# pvscan --cache /dev/sdf
# vgscan
   Reading all physical volumes.  This may take a while...
   Duplicate of PV fEGbBn-tbIp-rL7y-m22b-1rQh-r9i5-Qwlqz7 dev /dev/sdf
exists on unknown device 8:0
   Found volume group "xenpc1" using metadata type lvm2

Now I was able to activate it again and it was no longer flagged as
partial (but now it is duplicate).

The unknown device 8:0 is clearly going to be /dev/sda, which is no
longer there.

How can I dump this reference to 8:0 or should something else be done?

Oh right.... pvscan --cache without a parameter....

I wonder if I can run this while the thing is still activated....

I was beginning to think there'd be some hidden filter rule, but it was
"just" the cache.

Should this thing be automatically resolved? Is running pvscan --cache
enough?



------------------------------

Message: 2
Date: Mon, 15 Aug 2016 15:38:06 +0200
From: Xen <list@xenhideout.nl>
To: linux-lvm@redhat.com
Subject: Re: [linux-lvm] lvm2 raid volumes
Message-ID: <e2f9476f73b7ab05cc1e7a21643ed29e@dds.nl>
Content-Type: text/plain; charset=US-ASCII; format=flowed

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.



------------------------------

Message: 3
Date: Tue, 16 Aug 2016 11:44:23 +0200
From: Zdenek Kabelac <zdenek.kabelac@gmail.com>
To: LVM general discussion and development <linux-lvm@redhat.com>,
        stuart@gathman.org
Subject: Re: [linux-lvm] Snapshots & data security
Message-ID: <56821cec-70f8-086a-7e5b-6db8f0a9b780@gmail.com>
Content-Type: text/plain; charset=windows-1252; format=flowed

Dne 27.7.2016 v 21:17 Stuart Gathman napsal(a):
> On 07/19/2016 11:28 AM, Scott Sullivan wrote:
>>
>> Could someone please clarify if there is a legitimate reason to worry
>> about data security of a old (removed) LVM snapshot?
>>
>> For example, when you lvremove a LVM snapshot, is it possible for data
>> to be recovered if you create another LVM and it happens to go into
>> the same area as the old snapshot we lvremoved?
>>
>> If this helps clarify, do we have to worry about security scrubbing a
>> LVM snapshot for data security ?
>>
> Another idea: if your VG is on SSD, and properly aligned, then DISCARD
> on the new LV will effectively zero it as far as any guest VMs are
> concerned.  (The data is still on the flash until erased by the
> firmware, of course.)  If VG and PE size do not align with the SSD erase
> block, then you can still zero the "edges" of the new LV, which is much
> faster (and less wear on the SSD) than zeroing the whole thing.  You
> could always read-verify that the data is actually all zero.

Yes - as already suggested -  once you create a new LV -
you can  'blkdicard /dev/vg/lv'

Note - SSD may not always ensure blocks are zeroed - they could just
move trimmed block into reuse list with undefined content.

Anyway - lvm2 is not tool for data protection and it's upto system admin
to ensure there are no data leaks.

So pick the solution which fits best your needs - lvm2 provides all the
tooling for it.

Regards

Zdenek



------------------------------

Message: 4
Date: Thu, 25 Aug 2016 09:50:24 +0800
From: su liu <liusu8788@gmail.com>
To: linux-lvm <linux-lvm@redhat.com>
Subject: [linux-lvm] lvm2 cluster aware
Message-ID:
        <CAN2gjWSEzL+M45UGFEkEA_i5bgNpKLXTQ+DAMPJjJJvBBvaTKQ@mail.gmail.com>
Content-Type: text/plain; charset="utf-8"

I have a question about lvm2 cluster, The scene is that I try to imitate
FCSAN by mapping a rbd volume to two compute node, Then I using the rbd
volume to  create a PV and VG.I stoped the lvmetad daemon on the compute
nodes. Then I find that when I operating the VG on one compute node, the
changes can also be aware on another compute nodes.

But this docment(http://www.tldp.org/HOWTO/LVM-HOWTO/sharinglvm1.html? says
that "*LVM is not cluster aware".*

My question is that can I use the method to achieve the case that I create
or delete lv on one node whlie other compute node can using the lvs?

Can anybody explain this?

thx very much!
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Message: 5
Date: Thu, 25 Aug 2016 03:37:08 -0400
From: Digimer <lists@alteeve.ca>
To: LVM general discussion and development <linux-lvm@redhat.com>
Subject: Re: [linux-lvm] lvm2 cluster aware
Message-ID: <a0c7bedf-23d1-26c5-3853-0bd36f528185@alteeve.ca>
Content-Type: text/plain; charset=UTF-8

On 24/08/16 09:50 PM, su liu wrote:
> I have a question about lvm2 cluster, The scene is that I try to imitate
> FCSAN by mapping a rbd volume to two compute node, Then I using the rbd
> volume to  create a PV and VG.I stoped the lvmetad daemon on the compute
> nodes. Then I find that when I operating the VG on one compute node, the
> changes can also be aware on another compute nodes.
>
> But this docment(http://www.tldp.org/HOWTO/LVM-HOWTO
> /sharinglvm1.html? says that "*LVM is not cluster aware".*
>
> My question is that can I use the method to achieve the case that I
> create or delete lv on one node whlie other compute node can using the lvs?
>
> Can anybody explain this?
>
> thx very much!

You can use DLM (distributed lock manager) to provide cluster locking to
LVM (locking_type = 3 via clvmd). This requires a cluster though, which
you can get with corosync + pacemaker (and use stonith!).

Further details/advice requires more understanding of your environment
and use-case. Feel free to pop over to Clusterlabs[1], as many of us do
this setup regularly. I use clustered LVM in all our HA setups and have
done so successfully for years.

digimer

1. http://clusterlabs.org/mailman/listinfo/users - freenode #clusterlabs

--
Digimer
Papers and Projects: https://alteeve.ca/w/
What if the cure for cancer is trapped in the mind of a person without
access to education?



------------------------------

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