[linux-lvm] Cache block size warning
ciprian.hacman at sematext.com
Thu Nov 19 09:14:28 UTC 2015
Thank you for the quick answer. Sounds easy to implement if needed.
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On Thu, Nov 19, 2015 at 10:56 AM, Zdenek Kabelac <zdenek.kabelac at gmail.com>
> Dne 19.11.2015 v 08:27 Ciprian Hacman napsal(a):
>> We are configuring lvm with SSD caching on some of our boxes in AWS. When
>> 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
>> 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.
> linux-lvm mailing list
> linux-lvm at redhat.com
> read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
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