[linux-lvm] Cache block size warning

[Ciprian Hacman]

Thank you for the quick answer. Sounds easy to implement if needed.

Ciprian
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On Thu, Nov 19, 2015 at 10:56 AM, Zdenek Kabelac <zdenek.kabelac at gmail.com>
wrote:

> Dne 19.11.2015 v 08:27 Ciprian Hacman napsal(a):
>
>> Hi,
>>
>> We are configuring lvm with SSD caching on some of our boxes in AWS. When
>> the
>> cache is initialised, we see this in logs:
>>
>>     device-mapper*: cache: You have created a cache device with a lot of
>>     individual cache blocks (4915200)*
>>
>>     *               All these mappings can consume a lot of kernel
>> memory, and
>>     take some time to read/write.*
>>
>>     *               Please consider increasing the cache block size to
>> reduce
>>     the overall cache block count.*
>>
>>
>> Is this something to worry? If so, how can we improve it?
>>
>>
> If you have lots of kernel memory - it's probably ok.
> Otherwise you may try to use bigger chunk size.
>
> e.g.  --chunksize 512K   or even more:
>
> lvcreate --type cache-pool -L300G vg/cpool
>
> lvcreate -H --chunksize 512K -L1.5T   --name data  vg/cpool
>
> It's possible future version of lvm2 will try to create this by default.
>
> Zdenek
>
>
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>
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