[linux-lvm] LVM cache/dm-cache questions.

[linux-lvm] LVM cache/dm-cache questions.

[sergei]

Hi,

I have a few simple questions regarding relatively new feature LVM 
cache/dm-cache.

 From second hand information on internet, it appears that you cannot 
resize cached volume.
Please correct me if I am wrong: to resize a cached volume, one needs to 
lvremove the cache, resize and recreate the cache?

In scenario where cache device fails, how safe is the data on the cached 
LVM?

Is it possible to make snapshots of the cached device?

Before I test these things I will need to upgrade distribution (as the 
release I am on does not have the LVM cache), which means switching to 
systemd (I would rather avoid, if LVM cache does not fail gracefully).

Thank you very much!

Sergei.

Re: [linux-lvm] LVM cache/dm-cache questions.

[Brassow Jonathan]

> On Jun 11, 2016, at 7:36 PM, sergei <sergei.franco@gmail.com> wrote:
> 
> Hi,
> 
> I have a few simple questions regarding relatively new feature LVM cache/dm-cache.
> 
> From second hand information on internet, it appears that you cannot resize cached volume.
> Please correct me if I am wrong: to resize a cached volume, one needs to lvremove the cache, resize and recreate the cache?

This is true at the moment.  You are likely to be able to simply resize online in the future.

> In scenario where cache device fails, how safe is the data on the cached LVM?

If you are using writethrough, quite safe.  If you are using ‘writeback’, probably not (RAID for your cache in this case would probably be wise).

> Is it possible to make snapshots of the cached device?

easy answer is “no”.

complicated answer includes a ‘yes’.  You can cache a poolDataLV, then your thinLV and all its thinSnaps would be cached.

 brassow

Re: [linux-lvm] LVM cache/dm-cache questions.

[Sergei Franco]

Thank you!

That clears up a few questions!


Regards.

Sergei.

On 21 June 2016 at 04:27, Brassow Jonathan <jbrassow@redhat.com> wrote:
>
>> On Jun 11, 2016, at 7:36 PM, sergei <sergei.franco@gmail.com> wrote:
>>
>> Hi,
>>
>> I have a few simple questions regarding relatively new feature LVM cache/dm-cache.
>>
>> From second hand information on internet, it appears that you cannot resize cached volume.
>> Please correct me if I am wrong: to resize a cached volume, one needs to lvremove the cache, resize and recreate the cache?
>
> This is true at the moment.  You are likely to be able to simply resize online in the future.
>
>> In scenario where cache device fails, how safe is the data on the cached LVM?
>
> If you are using writethrough, quite safe.  If you are using ‘writeback’, probably not (RAID for your cache in this case would probably be wise).
>
>> Is it possible to make snapshots of the cached device?
>
> easy answer is “no”.
>
> complicated answer includes a ‘yes’.  You can cache a poolDataLV, then your thinLV and all its thinSnaps would be cached.
>
>  brassow
>
> _______________________________________________
> linux-lvm mailing list
> linux-lvm@redhat.com
> https://www.redhat.com/mailman/listinfo/linux-lvm
> read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/

Re: [linux-lvm] LVM cache/dm-cache questions.

[lejeczek]

question I'd like to ask is: how to LUKS encrypt cache pool LV ?

many thanks.
L.

On 20/06/16 17:27, Brassow Jonathan wrote:
>> On Jun 11, 2016, at 7:36 PM, sergei <sergei.franco@gmail.com> wrote:
>>
>> Hi,
>>
>> I have a few simple questions regarding relatively new feature LVM cache/dm-cache.
>>
>>  From second hand information on internet, it appears that you cannot resize cached volume.
>> Please correct me if I am wrong: to resize a cached volume, one needs to lvremove the cache, resize and recreate the cache?
> This is true at the moment.  You are likely to be able to simply resize online in the future.
>
>> In scenario where cache device fails, how safe is the data on the cached LVM?
> If you are using writethrough, quite safe.  If you are using ‘writeback’, probably not (RAID for your cache in this case would probably be wise).
>
>> Is it possible to make snapshots of the cached device?
> easy answer is “no”.
>
> complicated answer includes a ‘yes’.  You can cache a poolDataLV, then your thinLV and all its thinSnaps would be cached.
>
>   brassow
>
> _______________________________________________
> linux-lvm mailing list
> linux-lvm@redhat.com
> https://www.redhat.com/mailman/listinfo/linux-lvm
> read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/

Re: [linux-lvm] LVM cache/dm-cache questions.

[Xen]

lejeczek schreef op 25-08-2016 13:51:
> question I'd like to ask is: how to LUKS encrypt cache pool LV ?
> 
> many thanks.
> L.

In general without being any expert here you will need to encrypt the 
origin device (PV) on which it resides and likely also the PV of the 
cache pool itself. It's no different from any other volume you would 
use.

You can allow LUKS to pass-through discards if you open the volume with 
--allow-discards on the cryptsetup prompt (command).

In case you have an SSD underneath. It was said that the cache itself 
does not utilize discards just yet, but that it was in the planning.

Re: [linux-lvm] LVM cache/dm-cache questions.

[lejeczek]

well, I prefer to encrypt LV itself, and I'm trying the same 
what worked always with my "regular" LVs, yet - "cache pools 
LVs" fail to encrypt with: Command failed with code 22.



On 25/08/16 15:47, Xen wrote:
> lejeczek schreef op 25-08-2016 13:51:
>> question I'd like to ask is: how to LUKS encrypt cache 
>> pool LV ?
>>
>> many thanks.
>> L.
>
> In general without being any expert here you will need to 
> encrypt the origin device (PV) on which it resides and 
> likely also the PV of the cache pool itself. It's no 
> different from any other volume you would use.
>
> You can allow LUKS to pass-through discards if you open 
> the volume with --allow-discards on the cryptsetup prompt 
> (command).
>
> In case you have an SSD underneath. It was said that the 
> cache itself does not utilize discards just yet, but that 
> it was in the planning.
>
> _______________________________________________
> linux-lvm mailing list
> linux-lvm@redhat.com
> https://www.redhat.com/mailman/listinfo/linux-lvm
> read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/

Re: [linux-lvm] LVM cache/dm-cache questions.

[Xen]

lejeczek schreef op 26-08-2016 14:45:
> well, I prefer to encrypt LV itself, and I'm trying the same what
> worked always with my "regular" LVs, yet - "cache pools LVs" fail to
> encrypt with: Command failed with code 22.

If you are going to encrypt an LV it will no longer be an LV but an 
(opened) LUKS container.

Re: [linux-lvm] LVM cache/dm-cache questions.

[lejeczek]

whatever you might call it, it works, luks encrypting, 
opening & mounting @boot - so I only wonder (which was my 
question) why not cache pool LVs. Is it not supported...
would be great if a developer sees this question, I'm not 
sure jut yet about filing a bug report.

On 26/08/16 14:28, Xen wrote:
> lejeczek schreef op 26-08-2016 14:45:
>> well, I prefer to encrypt LV itself, and I'm trying the 
>> same what
>> worked always with my "regular" LVs, yet - "cache pools 
>> LVs" fail to
>> encrypt with: Command failed with code 22.
>
> If you are going to encrypt an LV it will no longer be an 
> LV but an (opened) LUKS container.
>
> _______________________________________________
> linux-lvm mailing list
> linux-lvm@redhat.com
> https://www.redhat.com/mailman/listinfo/linux-lvm
> read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/

Re: [linux-lvm] LVM cache/dm-cache questions.

[Ondrej Kozina]

On 08/26/2016 04:01 PM, lejeczek wrote:
> whatever you might call it, it works, luks encrypting,
> opening & mounting @boot - so I only wonder (which was my
> question) why not cache pool LVs. Is it not supported...
> would be great if a developer sees this question, I'm not
> sure jut yet about filing a bug report.

In general LVM2 doesn't auto-activate or interpret unknown device types. 
LUKS header is considered unknown from LVM2 perspective. Simply put LVM2 
doesn't understand LUKS header data. Not sure what you tried to do with 
cache pool LV, but in my opinion any effort to encrypt (live or 
detached) cache pool LV may end with severe data corruption...

As of now I think you have in general two options:

a) encrypt both PVs because obviously if you only encrypt the origin PV 
you end up with decrypted plaintext data stored in cache pool. Probably 
this is the exact scenario you were about to avoid?

Unfortunately a) is suboptimal with regard to performance since you'd 
perform the encryption of data blocks twice.

Option b): encrypt the top level LV (the one constructed from both cache 
and origin LV). This way ciphertext would be stored twice in cache PV 
and origin PV but the encryption would be performed only once.

Regards
Ondrej

Re: [linux-lvm] LVM cache/dm-cache questions.

[lejeczek]

On 26/08/16 15:45, Ondrej Kozina wrote:
> On 08/26/2016 04:01 PM, lejeczek wrote:
>> whatever you might call it, it works, luks encrypting,
>> opening & mounting @boot - so I only wonder (which was my
>> question) why not cache pool LVs. Is it not supported...
>> would be great if a developer sees this question, I'm not
>> sure jut yet about filing a bug report.
>
> In general LVM2 doesn't auto-activate or interpret unknown 
> device types. LUKS header is considered unknown from LVM2 
> perspective. Simply put LVM2 doesn't understand LUKS 
> header data. Not sure what you tried to do with cache pool 
> LV, but in my opinion any effort to encrypt (live or 
> detached) cache pool LV may end with severe data 
> corruption...
>
> As of now I think you have in general two options:
>
> a) encrypt both PVs because obviously if you only encrypt 
> the origin PV you end up with decrypted plaintext data 
> stored in cache pool. Probably this is the exact scenario 
> you were about to avoid?
>
> Unfortunately a) is suboptimal with regard to performance 
> since you'd perform the encryption of data blocks twice.
>
> Option b): encrypt the top level LV (the one constructed 
> from both cache and origin LV). This way ciphertext would 
> be stored twice in cache PV and origin PV but the 
> encryption would be performed only once.
>
gee, guys, thanks Ondrej,
this I was saying from the beginning did not work - option b 
- does not work. I can Not encrypt top level cache pool LV.
It does work with any other LV I have, but cache pool fails 
(like I said earlier) with:

Command failed with code 22.

And me speculating on my own - whether it is a bug or just 
limitation of implementation (Centos 7.2, 
lvm2-2.02.130-5.el7_2.4.x86_64, 
cryptsetup-1.6.7-1.el7.x86_64)- I thought instead I should 
seek clarification.

> Regards
> Ondrej
>
> _______________________________________________
> linux-lvm mailing list
> linux-lvm@redhat.com
> https://www.redhat.com/mailman/listinfo/linux-lvm
> read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/

Re: [linux-lvm] LVM cache/dm-cache questions.

[Ondrej Kozina]

On 08/29/2016 11:42 AM, lejeczek wrote:
>
>
> On 26/08/16 15:45, Ondrej Kozina wrote:
>> On 08/26/2016 04:01 PM, lejeczek wrote:
>>> whatever you might call it, it works, luks encrypting,
>>> opening & mounting @boot - so I only wonder (which was my
>>> question) why not cache pool LVs. Is it not supported...
>>> would be great if a developer sees this question, I'm not
>>> sure jut yet about filing a bug report.
>>
>> In general LVM2 doesn't auto-activate or interpret unknown
>> device types. LUKS header is considered unknown from LVM2
>> perspective. Simply put LVM2 doesn't understand LUKS
>> header data. Not sure what you tried to do with cache pool
>> LV, but in my opinion any effort to encrypt (live or
>> detached) cache pool LV may end with severe data
>> corruption...
>>
>> As of now I think you have in general two options:
>>
>> a) encrypt both PVs because obviously if you only encrypt
>> the origin PV you end up with decrypted plaintext data
>> stored in cache pool. Probably this is the exact scenario
>> you were about to avoid?
>>
>> Unfortunately a) is suboptimal with regard to performance
>> since you'd perform the encryption of data blocks twice.
>>
>> Option b): encrypt the top level LV (the one constructed
>> from both cache and origin LV). This way ciphertext would
>> be stored twice in cache PV and origin PV but the
>> encryption would be performed only once.
>>
> gee, guys, thanks Ondrej,
> this I was saying from the beginning did not work - option b
> - does not work. I can Not encrypt top level cache pool LV.
> It does work with any other LV I have, but cache pool fails
> (like I said earlier) with:
>
> Command failed with code 22.

Could you post here 'lsblk' and 'lvs' output together with exact 
cryptsetup command you have executed to luksFormat your top level cached 
LV? Please add also --debug option among your original cryptsetup options.

Regards
Ondrej

Re: [linux-lvm] LVM cache/dm-cache questions.

[lejeczek]

$ lvs -a h200front
   LV                      VG        Attr       LSize   Pool 
Origin    Data%  Meta%  Move Log Cpy%Sync Convert
   0                       h200front Cwi-aoC---   9.10t 
[cache0] [0_corig] 100.00 8.18            0.00
   [0_corig]               h200front rwi-aoC--- 
9.10t                                           100.00
   [0_corig_rimage_0]      h200front iwi-aor--- 1.82t
   [0_corig_rimage_1]      h200front iwi-aor--- 1.82t
   [0_corig_rimage_2]      h200front iwi-aor--- 1.82t
   [0_corig_rimage_3]      h200front iwi-aor--- 1.82t
   [0_corig_rimage_4]      h200front iwi-aor--- 1.82t
   [0_corig_rimage_5]      h200front iwi-aor--- 1.82t
   [0_corig_rmeta_0]       h200front ewi-aor--- 4.00m
   [0_corig_rmeta_1]       h200front ewi-aor--- 4.00m
   [0_corig_rmeta_2]       h200front ewi-aor--- 4.00m
   [0_corig_rmeta_3]       h200front ewi-aor--- 4.00m
   [0_corig_rmeta_4]       h200front ewi-aor--- 4.00m
   [0_corig_rmeta_5]       h200front ewi-aor--- 4.00m
   [cache0]                h200front Cwi---C--- 
220.00g                    100.00 8.18            0.00
   [cache0_cdata]          h200front Cwi-aor--- 
220.00g                                           100.00
   [cache0_cdata_rimage_0] h200front iwi-aor--- 220.00g
   [cache0_cdata_rimage_1] h200front iwi-aor--- 220.00g
   [cache0_cdata_rmeta_0]  h200front ewi-aor--- 4.00m
   [cache0_cdata_rmeta_1]  h200front ewi-aor--- 4.00m
   [cache0_cmeta]          h200front ewi-aor--- 
512.00m                                           100.00
   [cache0_cmeta_rimage_0] h200front iwi-aor--- 512.00m
   [cache0_cmeta_rimage_1] h200front iwi-aor--- 512.00m
   [cache0_cmeta_rmeta_0]  h200front ewi-aor--- 4.00m
   [cache0_cmeta_rmeta_1]  h200front ewi-aor--- 4.00m
   [lvol0_pmspare]         h200front ewi------- 512.00m

I cannot debug now as for now I've given up the idea to 
encrypt this LV, but  I would say is should be easily 
reproducible (maybe even waste of time looking at my setup) 
I simply tried:

  cryptsetup -v luksFormat /dev/mapper/h200front-0

and that works(ed) with "regurlar" LVs.

$ lsblk
NAME                              MAJ:MIN RM   SIZE RO TYPE 
MOUNTPOINT
sda                                 8:0    0 238.5G  0 disk
├─sda1                              8:1    0     1G  0 part  
/boot
└─sda2                              8:2    0 237.5G  0 part
   ├─SL-root                       253:0    0   150G  0 lvm   /
   └─SL-home                       253:1    0    10G  0 lvm
sdb                                 8:16   0 223.6G  0 disk
├─h200front-cache0_cdata_rmeta_0  253:4    0     4M  0 lvm
│ └─h200front-cache0_cdata        253:8    0   220G  0 lvm
│   └─h200front-0                 253:29   0   9.1T  0 lvm
├─h200front-cache0_cdata_rimage_0 253:5    0   220G  0 lvm
│ └─h200front-cache0_cdata        253:8    0   220G  0 lvm
│   └─h200front-0                 253:29   0   9.1T  0 lvm
├─h200front-cache0_cmeta_rmeta_0  253:9    0     4M  0 lvm
│ └─h200front-cache0_cmeta        253:13   0   512M  0 lvm
│   └─h200front-0                 253:29   0   9.1T  0 lvm
└─h200front-cache0_cmeta_rimage_0 253:10   0   512M  0 lvm
   └─h200front-cache0_cmeta        253:13   0   512M  0 lvm
     └─h200front-0                 253:29   0   9.1T  0 lvm
sdc                                 8:32   0 223.6G  0 disk
├─h200front-cache0_cdata_rmeta_1  253:6    0     4M  0 lvm
│ └─h200front-cache0_cdata        253:8    0   220G  0 lvm
│   └─h200front-0                 253:29   0   9.1T  0 lvm
├─h200front-cache0_cdata_rimage_1 253:7    0   220G  0 lvm
│ └─h200front-cache0_cdata        253:8    0   220G  0 lvm
│   └─h200front-0                 253:29   0   9.1T  0 lvm
├─h200front-cache0_cmeta_rmeta_1  253:11   0     4M  0 lvm
│ └─h200front-cache0_cmeta        253:13   0   512M  0 lvm
│   └─h200front-0                 253:29   0   9.1T  0 lvm
└─h200front-cache0_cmeta_rimage_1 253:12   0   512M  0 lvm
   └─h200front-cache0_cmeta        253:13   0   512M  0 lvm
     └─h200front-0                 253:29   0   9.1T  0 lvm
sdd                                 8:48   0 894.3G  0 disk
└─h300Int1-0                      253:2    0   1.8T  0 lvm
   └─h300Int1.0_crypt              253:27   0   1.8T  0 
crypt /__.aLocalStorages/2
sde                                 8:64   0 894.3G  0 disk
└─h300Int1-0                      253:2    0   1.8T  0 lvm
   └─h300Int1.0_crypt              253:27   0   1.8T  0 
crypt /__.aLocalStorages/2
sdf                                 8:80   0 447.1G  0 disk
└─h300Int0-0                      253:3    0   1.3T  0 lvm
   └─h300Int0.0_crypt              253:28   0   1.3T  0 
crypt /__.aLocalStorages/1
sdg                                 8:96   0 447.1G  0 disk
└─h300Int0-0                      253:3    0   1.3T  0 lvm
   └─h300Int0.0_crypt              253:28   0   1.3T  0 
crypt /__.aLocalStorages/1
sdh                                 8:112  0 447.1G  0 disk
└─h300Int0-0                      253:3    0   1.3T  0 lvm
   └─h300Int0.0_crypt              253:28   0   1.3T  0 
crypt /__.aLocalStorages/1
sdi                                 8:128  0   1.8T  0 disk
├─h200front-0_corig_rmeta_0       253:14   0     4M  0 lvm
│ └─h200front-0_corig             253:26   0   9.1T  0 lvm
│   └─h200front-0                 253:29   0   9.1T  0 lvm
└─h200front-0_corig_rimage_0      253:15   0   1.8T  0 lvm
   └─h200front-0_corig             253:26   0   9.1T  0 lvm
     └─h200front-0                 253:29   0   9.1T  0 lvm
sdj                                 8:144  0   1.8T  0 disk
├─h200front-0_corig_rmeta_1       253:16   0     4M  0 lvm
│ └─h200front-0_corig             253:26   0   9.1T  0 lvm
│   └─h200front-0                 253:29   0   9.1T  0 lvm
└─h200front-0_corig_rimage_1      253:17   0   1.8T  0 lvm
   └─h200front-0_corig             253:26   0   9.1T  0 lvm
     └─h200front-0                 253:29   0   9.1T  0 lvm
sdk                                 8:160  0   1.8T  0 disk
├─h200front-0_corig_rmeta_2       253:18   0     4M  0 lvm
│ └─h200front-0_corig             253:26   0   9.1T  0 lvm
│   └─h200front-0                 253:29   0   9.1T  0 lvm
└─h200front-0_corig_rimage_2      253:19   0   1.8T  0 lvm
   └─h200front-0_corig             253:26   0   9.1T  0 lvm
     └─h200front-0                 253:29   0   9.1T  0 lvm
sdl                                 8:176  0   1.8T  0 disk
├─h200front-0_corig_rmeta_3       253:20   0     4M  0 lvm
│ └─h200front-0_corig             253:26   0   9.1T  0 lvm
│   └─h200front-0                 253:29   0   9.1T  0 lvm
└─h200front-0_corig_rimage_3      253:21   0   1.8T  0 lvm
   └─h200front-0_corig             253:26   0   9.1T  0 lvm
     └─h200front-0                 253:29   0   9.1T  0 lvm
sdm                                 8:192  0   1.8T  0 disk
├─h200front-0_corig_rmeta_4       253:22   0     4M  0 lvm
│ └─h200front-0_corig             253:26   0   9.1T  0 lvm
│   └─h200front-0                 253:29   0   9.1T  0 lvm
└─h200front-0_corig_rimage_4      253:23   0   1.8T  0 lvm
   └─h200front-0_corig             253:26   0   9.1T  0 lvm
     └─h200front-0                 253:29   0   9.1T  0 lvm
sdn                                 8:208  0   1.8T  0 disk
├─h200front-0_corig_rmeta_5       253:24   0     4M  0 lvm
│ └─h200front-0_corig             253:26   0   9.1T  0 lvm
│   └─h200front-0                 253:29   0   9.1T  0 lvm
└─h200front-0_corig_rimage_5      253:25   0   1.8T  0 lvm
   └─h200front-0_corig             253:26   0   9.1T  0 lvm
     └─h200front-0                 253:29   0   9.1T  0 lvm
sdo                                 8:224  0   9.1T  0 disk 
/__.aLocalStorages/3

LV is working fine, being a host for all sorts of data, only 
cryptsetup does not work on it.
many thanks.



On 29/08/16 12:22, Ondrej Kozina wrote:
> On 08/29/2016 11:42 AM, lejeczek wrote:
>>
>>
>> On 26/08/16 15:45, Ondrej Kozina wrote:
>>> On 08/26/2016 04:01 PM, lejeczek wrote:
>>>> whatever you might call it, it works, luks encrypting,
>>>> opening & mounting @boot - so I only wonder (which was my
>>>> question) why not cache pool LVs. Is it not supported...
>>>> would be great if a developer sees this question, I'm not
>>>> sure jut yet about filing a bug report.
>>>
>>> In general LVM2 doesn't auto-activate or interpret unknown
>>> device types. LUKS header is considered unknown from LVM2
>>> perspective. Simply put LVM2 doesn't understand LUKS
>>> header data. Not sure what you tried to do with cache pool
>>> LV, but in my opinion any effort to encrypt (live or
>>> detached) cache pool LV may end with severe data
>>> corruption...
>>>
>>> As of now I think you have in general two options:
>>>
>>> a) encrypt both PVs because obviously if you only encrypt
>>> the origin PV you end up with decrypted plaintext data
>>> stored in cache pool. Probably this is the exact scenario
>>> you were about to avoid?
>>>
>>> Unfortunately a) is suboptimal with regard to performance
>>> since you'd perform the encryption of data blocks twice.
>>>
>>> Option b): encrypt the top level LV (the one constructed
>>> from both cache and origin LV). This way ciphertext would
>>> be stored twice in cache PV and origin PV but the
>>> encryption would be performed only once.
>>>
>> gee, guys, thanks Ondrej,
>> this I was saying from the beginning did not work - option b
>> - does not work. I can Not encrypt top level cache pool LV.
>> It does work with any other LV I have, but cache pool fails
>> (like I said earlier) with:
>>
>> Command failed with code 22.
>
> Could you post here 'lsblk' and 'lvs' output together with 
> exact cryptsetup command you have executed to luksFormat 
> your top level cached LV? Please add also --debug option 
> among your original cryptsetup options.
>
> Regards
> Ondrej
>
>
> _______________________________________________
> linux-lvm mailing list
> linux-lvm@redhat.com
> https://www.redhat.com/mailman/listinfo/linux-lvm
> read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/

Re: [linux-lvm] LVM cache/dm-cache questions.

[Ondrej Kozina]

Thank you for the lsblk and lvs output. At least now we know that raid 
is somehow involved in the setup...

On 08/29/2016 04:22 PM, lejeczek wrote:
> I cannot debug now as for now I've given up the idea to
> encrypt this LV, but  I would say is should be easily
> reproducible (maybe even waste of time looking at my setup)
> I simply tried:

Well, without the debug output from cryptsetup I can't be of any more 
help, I'm sorry. It's like starring into crystal ball guessing what may 
have gone wrong. The -22 error code is general "wrong parameters" 
answer. I don't even know if cryptsetup has got into code path where 
it's supposed to open the device for write.

But let me give it one last shot. Did you by any chance end up with 22 
right after the prompt:

"Are you sure? (Type uppercase yes):"

If so, are you sure that your answer was 'YES' instead of lowercase 'yes'?

Regards
Ondrej

Re: [linux-lvm] LVM cache/dm-cache questions.

[lejeczek]

now when you say that - (I) believe it or not - I think it's 
possible. I cannot test it, for now the LV is in production 
but! I few days ago introduced an external usb keboard which 
has not LED indicators at all and now when I play with it it 
seems there might be problem on my f24, maybe the 
drivers(?). Gee, open source with all its greatness and the 
luck of officially Christened, own hardware(laptop) can be a 
reason of great frustration sometimes.
I'll put together another cache pool some days and then 
shall provide clarification to my own frustration.


On 29/08/16 16:08, Ondrej Kozina wrote:
> Thank you for the lsblk and lvs output. At least now we 
> know that raid is somehow involved in the setup...
>
> On 08/29/2016 04:22 PM, lejeczek wrote:
>> I cannot debug now as for now I've given up the idea to
>> encrypt this LV, but  I would say is should be easily
>> reproducible (maybe even waste of time looking at my setup)
>> I simply tried:
>
> Well, without the debug output from cryptsetup I can't be 
> of any more help, I'm sorry. It's like starring into 
> crystal ball guessing what may have gone wrong. The -22 
> error code is general "wrong parameters" answer. I don't 
> even know if cryptsetup has got into code path where it's 
> supposed to open the device for write.
>
> But let me give it one last shot. Did you by any chance 
> end up with 22 right after the prompt:
>
> "Are you sure? (Type uppercase yes):"
>
> If so, are you sure that your answer was 'YES' instead of 
> lowercase 'yes'?
>
> Regards
> Ondrej
>
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Re: [linux-lvm] LVM cache/dm-cache questions.

[Xen]

lejeczek schreef op 29-08-2016 16:22:

> I cannot debug now as for now I've given up the idea to encrypt this
> LV, but  I would say is should be easily reproducible (maybe even
> waste of time looking at my setup)

I can definitely say I have encrypted a cached volume without issue.

I have had a disk with two cached volumes, if you want to know, both 
caches originating from the same SSD.

Main caches (main origin volume) were on a HDD in a simple regular 
non-thin LVM.

Re: [linux-lvm] LVM cache/dm-cache questions.

[Xen]

lejeczek schreef op 26-08-2016 16:01:
> whatever you might call it, it works, luks encrypting, opening &
> mounting @boot - so I only wonder (which was my question) why not
> cache pool LVs. Is it not supported...
> would be great if a developer sees this question, I'm not sure jut yet
> about filing a bug report.

Ondrej has it down.

You can only encrypt the combined volume, not the individual parts, 
unless you encrypt those at the PV level.