[linux-lvm] Cache block size warning
zdenek.kabelac at gmail.com
Thu Nov 19 08:56:41 UTC 2015
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 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.
More information about the linux-lvm