[linux-lvm] what todo with broken cachedev?

[linux-lvm] what todo with broken cachedev?

[Oliver Rath]

Hi list,

assuming a cached device mylv from /dev/sda1 with cachepool from
/dev/sdb1 (ssd i.e.):

If now the ssd crashes and the cachemode is "writethrough" i think,
there is no data loss for my lv's, right?

But then mylv runs without a cache device although the device is set in
metadata.

The command lvreduce cant remove the cache-attribut. vgreduce *could*
remove it, right? But only if there is no usage bei the cachepool-device
anymore.

Is there a solution for that?

Tfh!
Oliver

Re: [linux-lvm] what todo with broken cachedev?

[Zdenek Kabelac]

Dne 9.8.2014 19:25, Oliver Rath napsal(a):
> Hi list,
>
> assuming a cached device mylv from /dev/sda1 with cachepool from
> /dev/sdb1 (ssd i.e.):
>
> If now the ssd crashes and the cachemode is "writethrough" i think,
> there is no data loss for my lv's, right?
>
> But then mylv runs without a cache device although the device is set in
> metadata.
>
> The command lvreduce cant remove the cache-attribut. vgreduce *could*
> remove it, right? But only if there is no usage bei the cachepool-device
> anymore.
>
> Is there a solution for that?


Cache support is still experimental - so please open bugzillas
for your issues found on  bugzilla.redhat.com
(if you are not using Fedora/RHEL - use Fedora Rawhide for your reports)

I assume your problem is likely related to still missing repair support
for cached volumes.

You would need to use  cache utils  (cache_check, cache_repair, cache_dump...) 
to fix broken metadata.

Zdenek

Re: [linux-lvm] what todo with broken cachedev?

[Brassow Jonathan]

On Aug 11, 2014, at 7:55 AM, Zdenek Kabelac wrote:

> Dne 9.8.2014 19:25, Oliver Rath napsal(a):
>> Hi list,
>> 
>> assuming a cached device mylv from /dev/sda1 with cachepool from
>> /dev/sdb1 (ssd i.e.):
>> 
>> If now the ssd crashes and the cachemode is "writethrough" i think,
>> there is no data loss for my lv's, right?
>> 
>> But then mylv runs without a cache device although the device is set in
>> metadata.
>> 
>> The command lvreduce cant remove the cache-attribut. vgreduce *could*
>> remove it, right? But only if there is no usage bei the cachepool-device
>> anymore.
>> 
>> Is there a solution for that?
> 
> 
> Cache support is still experimental - so please open bugzillas
> for your issues found on  bugzilla.redhat.com
> (if you are not using Fedora/RHEL - use Fedora Rawhide for your reports)
> 
> I assume your problem is likely related to still missing repair support
> for cached volumes.
> 
> You would need to use  cache utils  (cache_check, cache_repair, cache_dump...) to fix broken metadata.

Also, it would be nice when using "writethrough" to have the option of abandoning the cache - making it a normal LV again.  If there is no way to get the SSD back, there is probably no point in fixing.  Operation might have to be forced if "writeback".

 brassow

Re: [linux-lvm] what todo with broken cachedev?

[Brassow Jonathan]

On Aug 19, 2014, at 6:41 PM, Brassow Jonathan wrote:

> 
> Also, it would be nice when using "writethrough" to have the option of abandoning the cache - making it a normal LV again.  If there is no way to get the SSD back, there is probably no point in fixing.  Operation might have to be forced if "writeback".

bug created.
https://bugzilla.redhat.com/show_bug.cgi?id=1131777