[linux-lvm] How to calculate the LVM SSD cache size?

[Zdenek Kabelac]

Dne 13.10.2014 v 14:20 Kees de Jong napsal(a):
> Hi,
>
>
>
> The documentation is not clear about how big the cache size should be
> for optimal performance. It only gives pointers about how big the meta
> data for the cache should be.
>
> "Create the cache metadata LV. This LV will hold cache pool metadata.
> The size of this LV should be 1000 times smaller than the cache data
> LV, with a minimum size of 8MiB."
>
> There is however an example in the man page with a 100GB OriginLV
> which apparently needs (at least) 10GB of cache size. But what is the
> math? I for example have 4 LV's I want to cache. 6GB, 60GB, 100GB and
> 2TB and I have a 240GB SSD which will act as the caching disk.
>
> Could someone please fill in the gaps here?
>
>

https://github.com/jthornber/thin-provisioning-tools/blob/master/caching/cache_metadata_size.cc

The recent lvm2 tools (git) should maintain the size of metadata device
at proper size for any given cache pool data device size.

Zdenek