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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