Re: dm-cache issue

[Alexander Pashaliyski <al.pashaliyski@gmail.com>]

On 11/14/2016 05:34 PM, Zdenek Kabelac wrote:
> Dne 14.11.2016 v 16:02 Alexander Pashaliyski napsal(a):
>> Hi guys,
>>
>>
>> I am in a process of evaluating dm-cache for our backup system.
>>
>> Currently I have an issue when restart the backup server. The server is
>> booting for hours, because of IO load. It seems is triggered a flush 
>> from SSD
>> disk (that is used for a cache device) to the raid controllers (they 
>> are with
>> slow SATA disks).
>> I have 10 cached logical volumes in *writethrough mode*, each with 2T 
>> of data
>> over 2 raid controllers. I use a single SSD disk for the cache.
>> The backup system is with lvm2-2.02.164-1 & kernel 4.4.30.
>>
>>
>> Do you have any ideas why such flush is triggered? In writethrough 
>> cache mode
>> we shouldn't have dirty blocks in the cache.
>>
>
> Hi
>
> Have you ensured there was proper shutdown ?
> Cache needs to be properly deactivated - if it's just turned off,
> all metadata are marked dirty.
>
>
> Regards
>
> Zdenek
>
Hi Zdenek,

Thank you for your answer.
Yes, I am sure. I have modified the lvm2 init script to de-activate all 
logical volumes and then volume groups, but the issue still persist.


Regards,
Alex